IP Addressing: IPv4 Addressing Configuration Guide
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CONTENTS
CHAPTER 1
Read Me First 1
CHAPTER 2
Configuring IPv4 Addresses 3
Finding Feature Information 3
Information About IP Addresses 4
Binary Numbering 4
IP Address Structure 6
IP Address Classes 7
IP Network Subnetting 9
IP Network Address Assignments 11
Classless Inter-Domain Routing 13
Prefixes 13
How to Configure IP Addresses 14
Establishing IP Connectivity to a Network by Assigning an IP Address to an Interface 14
Troubleshooting Tips 15
Increasing the Number of IP Hosts that Are Supported on a Network by Using Secondary IP
Addresses 15
Troubleshooting Tips 16
What to Do Next 17
Maximizing the Number of Available IP Subnets by Allowing the Use of IP Subnet Zero 17
Troubleshooting Tips 18
Specifying the Format of Network Masks 18
Specifying the Format in Which Netmasks Appear for the Current Session 19
Specifying the Format in Which Netmasks Appear for an Individual Line 19
Using IP Unnumbered Interfaces on Point-to-Point WAN Interfaces to Limit Number of IP
Addresses Required 20
IP Unnumbered Feature 20
Troubleshooting Tips 22
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Contents
Using IP addresses with 31-Bit Prefixes on Point-to-Point WAN Interfaces to Limit Number
of IP Addresses Required 22
RFC 3021 23
Troubleshooting Tips 25
Configuration Examples for IP Addresses 25
Example Establishing IP Connectivity to a Network by Assigning an IP Address to an
Interface 25
Example Increasing the Number of IP Hosts that are Supported on a Network by Using
Secondary IP Addresses 26
Example Using IP Unnumbered Interfaces on Point-to-Point WAN Interfaces to Limit
Number of IP Addresses Required 26
Example Using IP addresses with 31-Bit Prefixes on Point-to-Point WAN Interfaces to
Limit Number of IP Addresses Required 27
Example Maximizing the Number of Available IP Subnets by Allowing the Use of IP Subnet
Zero 27
Where to Go Next 27
Additional References 27
Feature Information for IP Addresses 29
CHAPTER 3
IP Overlapping Address Pools 31
Finding Feature Information 31
Restrictions for IP Overlapping Address Pools 31
Information About IP Overlapping Address Pools 32
Benefits 32
How IP Address Groups Work 32
How to Configure IP Overlapping Address Pools 32
Configuring and Verifying a Local Pool Group 32
Configuration Examples for Configuring IP Overlapping Address Pools 33
Define Local Address Pooling as the Global Default Mechanism Example 33
Configure Multiple Ranges of IP Addresses into One Pool Example 33
Additional References 34
Feature Information for Configuring IP Overlapping Address Pools 35
Glossary 36
CHAPTER 4
IP Unnumbered Ethernet Polling Support 37
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Contents
Finding Feature Information 37
Information About IP Unnumbered Ethernet Polling Support 37
IP Unnumbered Ethernet Polling Support Overview 37
How to Configure IP Unnumbered Ethernet Polling Support 38
Enabling Polling on an Ethernet Interface 38
Configuring the Queue Size and the Packet Rate for IP ARP Polling for Unnumbered
Interfaces 39
Verifying IP Unnumbered Ethernet Polling Support 40
Configuration Examples for IP Unnumbered Ethernet Polling Support 42
Example: Enabling Polling on an Ethernet Interface 42
Example: Configuring the Queue Size and the Packet Rate for IP ARP Polling for Unnumbered
Interfaces 42
Additional References 42
Feature Information for IP Unnumbered Ethernet Polling Support 43
CHAPTER 5
Auto-IP 45
Finding Feature Information 46
Prerequisites for Auto-IP 46
Restrictions for Auto-IP 46
Information About Auto-IP 47
Auto-IP Overview 47
Seed Device 49
Auto-IP Configuration for Inserting a Device into an Auto-IP Ring 50
Device Removal from an Auto-IP Ring 52
Conflict Resolution Using the Auto-Swap Technique 52
How to Configure Auto-IP 54
Configuring a Seed Device 54
Configuring the Auto-IP Functionality on Node Interfaces (for Inclusion in an Auto-IP
Ring) 57
Verifying and Troubleshooting Auto-IP 59
Configuration Examples for Auto-IP 61
Example: Configuring a Seed Device 61
Example: Configuring the Auto-IP Functionality on Node Interfaces (for Inclusion in an Auto-IP
Ring) 61
Additional References for Auto-IP 62
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Feature Information for Auto-IP 63
CHAPTER 6
Zero Touch Auto-IP 65
Finding Feature Information 65
Prerequisites for Zero Touch Auto-IP 66
Restrictions for Zero Touch Auto-IP 66
Information About Zero Touch Auto-IP 66
How to Configure Zero Touch Auto-IP 68
Associating an Auto-IP Server with an Autonomic Network 68
Enabling Auto Mode on Auto-IP Ring Ports 70
Configuring an Auto-IP Server and Reserving a Pool of IP Addresses on the Server 72
Configuring a Seed Port 73
Verifying and Troubleshooting Zero Touch Auto-IP 74
Configuration Examples for Zero Touch Auto-IP 77
Example: Associating an Auto-IP Server with an Autonomic Network 77
Example: Enabling Auto Mode on Auto-IP Ring Ports 77
Example: Configuring an Auto-IP Server and Reserving a Pool of IP Addresses on the
Server 77
Example: Configuring a Seed Port 77
Additional References for Zero Touch Auto-IP 78
Feature Information for Auto-IP 78
IP Addressing: IPv4 Addressing Configuration Guide
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CHAPTER
1
Read Me First
Important Information about Cisco IOS XE 16
Effective Cisco IOS XE Release 3.7.0E (for Catalyst Switching) and Cisco IOS XE Release 3.17S (for
Access and Edge Routing) the two releases evolve (merge) into a single version of converged release—the
Cisco IOS XE 16—providing one release covering the extensive range of access and edge products in the
Switching and Routing portfolio.
Note
The Feature Information table in the technology configuration guide mentions when a feature was
introduced. It might or might not mention when other platforms were supported for that feature. To
determine if a particular feature is supported on your platform, look at the technology configuration guides
posted on your product landing page. When a technology configuration guide is displayed on your product
landing page, it indicates that the feature is supported on that platform.
IP Addressing: IPv4 Addressing Configuration Guide
1
Read Me First
IP Addressing: IPv4 Addressing Configuration Guide
2
CHAPTER
2
Configuring IPv4 Addresses
This chapter contains information about, and instructions for configuring IPv4 addresses on interfaces that
are part of a networking device.
Note
All further references to IPv4 addresses in this document use only IP in the text, not IPv4.
• Finding Feature Information, page 3
• Information About IP Addresses, page 4
• How to Configure IP Addresses, page 14
• Configuration Examples for IP Addresses, page 25
• Where to Go Next, page 27
• Additional References, page 27
• Feature Information for IP Addresses, page 29
Finding Feature Information
Your software release may not support all the features documented in this module. For the latest caveats and
feature information, see Bug Search Tool and the release notes for your platform and software release. To
find information about the features documented in this module, and to see a list of the releases in which each
feature is supported, see the feature information table.
Use Cisco Feature Navigator to find information about platform support and Cisco software image support.
To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.
IP Addressing: IPv4 Addressing Configuration Guide
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Configuring IPv4 Addresses
Information About IP Addresses
Information About IP Addresses
Binary Numbering
IP addresses are 32 bits long. The 32 bits are divided into four octets (8-bits). A basic understanding of binary
numbering is very helpful if you are going to manage IP addresses in a network because changes in the values
of the 32 bits indicate either a different IP network address or IP host address.
A value in binary is represented by the number (0 or 1) in each position multiplied by the number 2 to the
power of the position of the number in sequence, starting with 0 and increasing to 7, working right to left.
The figure below is an example of an 8-digit binary number.
Figure 1: Example of an 8-digit Binary Number
IP Addressing: IPv4 Addressing Configuration Guide
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Configuring IPv4 Addresses
Binary Numbering
The figure below provides binary to decimal number conversion for 0 through 134.
Figure 2: Binary to Decimal Number Conversion for 0 to 134
IP Addressing: IPv4 Addressing Configuration Guide
5
Configuring IPv4 Addresses
IP Address Structure
The figure below provides binary to decimal number conversion for 135 through 255.
Figure 3: Binary to Decimal Number Conversion for 135 to 255
IP Address Structure
An IP host address identifies a device to which IP packets can be sent. An IP network address identifies a
specific network segment to which one or more hosts can be connected. The following are characteristics of
IP addresses:
• IP addresses are 32 bits long
• IP addresses are divided into four sections of one byte (octet) each
• IP addresses are typically written in a format known as dotted decimal
The table below shows some examples of IP addresses.
Table 1: Examples of IP Addresses
IP Addresses in Dotted Decimal
IP Addresses in Binary
10.34.216.75
00001010.00100010.11011000.01001011
172.16.89.34
10101100.00010000.01011001.00100010
192.168.100.4
11000000.10101000.01100100.00000100
IP Addressing: IPv4 Addressing Configuration Guide
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Configuring IPv4 Addresses
IP Address Classes
Note
The IP addresses in the table above are from RFC 1918, Address Allocation for Private Internets . These
IP addresses are not routable on the Internet. They are intended for use in private networks. For more
information on RFC1918, see http://www.ietf.org/rfc/rfc1918.txt .
IP addresses are further subdivided into two sections known as network and host. The division is accomplished
by arbitrarily ranges of IP addresses to classes. For more information see RFC 791 Internet Protocol at http:/
/www.ietf.org/rfc/rfc0791.txt .
IP Address Classes
In order to provide some structure to the way IP addresses are assigned, IP addresses are grouped into classes.
Each class has a range of IP addresses. The range of IP addresses in each class is determined by the number
of bits allocated to the network section of the 32-bit IP address. The number of bits allocated to the network
section is represented by a mask written in dotted decimal or with the abbreviation /n where n = the numbers
of bits in the mask.
The table below lists ranges of IP addresses by class and the masks associated with each class. The digits in
bold indicate the network section of the IP address for each class. The remaining digits are available for host
IP addresses. For example, IP address 10.90.45.1 with a mask of 255.0.0.0 is broken down into a network IP
address of 10.0.0.0 and a host IP address of 0.90.45.1.
Table 2: IP Address Ranges by Class with Masks
Class
Range
A (range/mask in dotted decimal)
0 .0.0.0 to 127.0.0.0/8 (255.0.0.0)
A (range in binary)
00000000 .00000000.00000000.00000000
to01111111.00000000.00000000.00000000
A (mask in binary)
11111111.00000000.00000000.00000000/8
B (range/mask in dotted decimal)
128 .0.0.0 to 191.255.0.0/16 (255.255.0.0)
B (range in binary)
10000000 .00000000.00000000.00000000
to10111111.11111111.00000000.00000000
B (mask in binary)
11111111 .11111111.00000000.00000000/16
C (range/mask in dotted decimal)
192 .0.0.0 to 223.255.255.0/24 (255.255.255.0)
C (range in binary)
11000000 .00000000.00000000.00000000
to11011111.11111111.11111111.00000000
C (mask in binary)
11111111.11111111.11111111.0000000/24
D1 (range/mask in dotted decimal)
224 .0.0.0 to 239.255.255.255/32 (255.255.255.255)
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Configuring IPv4 Addresses
IP Address Classes
Class
Range
D (range in binary)
11100000 .00000000.00000000.00000000
to11101111.11111111.11111111.11111111
D (mask in binary)
11111111.11111111.11111111.11111111/32
E2 (range/mask in dotted decimal)
240 .0.0.0 to 255.255.255.255/32 (255.255.255.255)
E (range in binary)
11110000 .00000000.00000000.00000000
to11111111.11111111.11111111.11111111
E (mask in binary)
11111111.11111111.11111111.11111111/32
1 Class D IP addresses are reserved for multicast applications.
2 Class E IP addresses are reserved for broadcast traffic.
Note
Some IP addresses in these ranges are reserved for special uses. For more information refer to RFC 3330,
Special-Use IP Addresses , at http://www.ietf.org/rfc/rfc3330.txt .
When a digit that falls within the network mask changes from 1 to 0 or 0 to 1 the network address is changed.
For example, if you change 10101100.00010000.01011001.00100010/16 to
10101100.00110000.01011001.00100010/16 you have changed the network address from 172.16.89.34/16
to 172.48.89.34/16.
When a digit that falls outside the network mask changes from 1 to 0 or 0 to 1 the host address is changed.
For example, if you change 10101100.00010000.01011001.00100010/16 to
10101100.00010000.01011001.00100011/16 you have changed the host address from 172.16.89.34/16 to
172.16.89.35/16.
Each class of IP address supports a specific range of IP network addresses and IP host addresses. The range
of IP network addresses available for each class is determined with the formula 2 to the power of the number
of available bits. In the case of class A addresses, the value of the first bit in the 1st octet (as shown in the
table above) is fixed at 0. This leaves 7 bits for creating additional network addresses. Therefore there are 128
IP network addresses available for class A (27 = 128).
The number of IP host addresses available for an IP address class is determined by the formula 2 to the power
of the number of available bits minus 2. There are 24 bits available in a class A addresses for IP host addresses.
Therefore there are 16,777,214 IP hosts addresses available for class A ((224) - 2 = 16,777,214)).
Note
The 2 is subtracted because there are 2 IP addresses that cannot be used for a host. The all 0’s host address
cannot be used because it is the same as the network address. For example, 10.0.0.0 cannot be both a IP
network address and an IP host address. The all 1’s address is a broadcast address that is used to reach all
hosts on the network. For example, an IP datagram addressed to 10.255.255.255 will be accepted by every
host on network 10.0.0.0.
The table below shows the network and host addresses available for each class of IP address.
IP Addressing: IPv4 Addressing Configuration Guide
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Configuring IPv4 Addresses
IP Network Subnetting
Table 3: Network and Host Addresses Available for Each Class of IP Address
Class
Network Addresses
Host Addresses
A
128
16,777,214
B
16,3843
65534
C
2,097,1524
254
3 Only 14 bits are available for class B IP network addresses because the first 2 bits are fixed at 10 as shown in Table 2 .
4 Only 21 bits are available for class C IP network addresses because the first 3 bits are fixed at 110 as shown in Table 2 .
IP Network Subnetting
The arbitrary subdivision of network and host bits in IP address classes resulted in an inefficient allocation
of IP space. For example, if your network has 16 separate physical segments you will need 16 IP network
addresses. If you use 16 class B IP network addresses, you would be able to support 65,534 hosts on each of
the physical segments. Your total number of supported host IP addresses is 1,048,544 (16 * 65,534 = 1,048,544).
Very few network technologies can scale to having 65,534 hosts on a single network segment. Very few
companies need 1,048,544 IP host addresses. This problem required the development of a new strategy that
permitted the subdivision of IP network addresses into smaller groupings of IP subnetwork addresses. This
strategy is known as subnetting.
If your network has 16 separate physical segments you will need 16 IP subnetwork addresses. This can be
accomplished with one class B IP address. For example, start with the class B IP address of 172.16.0.0 you
can reserve 4 bits from the third octet as subnet bits. This gives you 16 subnet IP addresses 24 = 16. The table
below shows the IP subnets for 172.16.0.0/20.
Table 4: Examples of IP Subnet Addresses using 172.16.0.0/20
Number
IP Subnet Addresses in Dotted
Decimal
IP Subnet Addresses in Binary
05
172.16.0.0
10101100.00010000.00000000.00000000
1
172.16.16.0
10101100.00010000.00010000.00000000
2
172.16.32.0
10101100.00010000.00100000.00000000
3
172.16.48.0
10101100.00010000.00110000.00000000
4
172.16.64.0
10101100.00010000.01000000.00000000
5
172.16.80.0
10101100.00010000.01010000.00000000
6
172.16.96.0
10101100.00010000.01100000.00000000
7
172.16.112.0
10101100.00010000.01110000.00000000
IP Addressing: IPv4 Addressing Configuration Guide
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Configuring IPv4 Addresses
IP Network Subnetting
Number
IP Subnet Addresses in Dotted
Decimal
IP Subnet Addresses in Binary
8
172.16.128.0
10101100.00010000.10000000.00000000
9
172.16.144.0
10101100.00010000.10010000.00000000
10
172.16.160.0
10101100.00010000.10100000.00000000
11
172.16.176.0
10101100.00010000.10110000.00000000
12
172.16.192.0
10101100.00010000.11000000.00000000
13
172.16.208.0
10101100.00010000.11010000.00000000
14
172.16.224.0
10101100.00010000.11100000.00000000
15
172.16.240.0
10101100.00010000.11110000.00000000
5 The first subnet that has all of the subnet bits set to 0 is referred to as subnet 0 . It is indistinguishable from the network address and must be used carefully.
When a digit that falls within the subnetwork (subnet) mask changes from 1 to 0 or 0 to 1 the subnetwork
address is changed. For example, if you change 10101100.00010000.01011001.00100010/20 to
10101100.00010000.01111001.00100010/20 you have changed the network address from 172.16.89.34/20
to 172.16.121.34/20.
When a digit that falls outside the subnet mask changes from 1 to 0 or 0 to 1 the host address is changed. For
example, if you change 10101100.00010000.01011001.00100010/20 to
10101100.00010000.01011001.00100011/20 you have changed the host address from 172.16.89.34/20 to
172.16.89.35/20.
Timesaver
To avoid having to do manual IP network, subnetwork, and host calculations, use one of the free IP subnet
calculators available on the Internet.
Some people get confused about the terms network address and subnet or subnetwork addresses and when to
use them. In the most general sense the term network address means “the IP address that routers use to route
traffic to a specific network segment so that the intended destination IP host on that segment can receive it”.
Therefore the term network address can apply to both non-subnetted and subnetted IP network addresses.
When you are troubleshooting problems with forwarding traffic from a router to a specific IP network address
that is actually a subnetted network address, it can help to be more specific by referring to the destination
network address as a subnet network address because some routing protocols handle advertising subnet network
routes differently from network routes. For example, the default behavior for RIP v2 is to automatically
summarize the subnet network addresses that it is connected to their non-subnetted network addresses
(172.16.32.0/24 is advertised by RIP v2 as 172.16.0.0/16) when sending routing updates to other routers.
Therefore the other routers might have knowledge of the IP network addresses in the network, but not the
subnetted network addresses of the IP network addresses.
IP Addressing: IPv4 Addressing Configuration Guide
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Configuring IPv4 Addresses
IP Network Address Assignments
Tip
The term IP address space is sometimes used to refer to a range of IP addresses. For example, “We have
to allocate a new IP network address to our network because we have used all of the available IP addresses
in the current IP address space”.
IP Network Address Assignments
Routers keep track of IP network addresses to understand the network IP topology (layer 3 of the OSI reference
model) of the network to ensure that IP traffic can be routed properly. In order for the routers to understand
the network layer (IP) topology, every individual physical network segment that is separated from any other
physical network segment by a router must have a unique IP network address.
The figure below shows an example of a simple network with correctly configured IP network addresses. The
routing table in R1 looks like the table below.
Table 5: Routing Table for a Correctly Configured Network
Interface Ethernet 0
Interface Ethernet 1
172.31.32.0/24 (Connected)
172.31.16.0/24 (Connected)
Figure 4: Correctly Configured Network
IP Addressing: IPv4 Addressing Configuration Guide
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Configuring IPv4 Addresses
IP Network Address Assignments
The figure below shows an example of a simple network with incorrectly configured IP network addresses.
The routing table in R1 looks like the table below. If the PC with IP address 172.31.32.3 attempts to send IP
traffic to the PC with IP address 172.31.32.54, router R1 cannot determine which interface that the PC with
IP address 172.31.32.54 is connected to.
Table 6: Routing Table in Router R1 for an Incorrectly Configured Network (Example 1)
Ethernet 0
Ethernet 1
172.31.32.0/24 (Connected)
172.31.32.0/24 (Connected)
Figure 5: Incorrectly Configured Network (Example 1)
To help prevent mistakes as shown in the figure above, Cisco IOS-based networking devices will not allow
you to configure the same IP network address on two or more interfaces in the router when IP routing is
enabled.
The only way to prevent the mistake shown in the figure below, where 172.16.31.0/24 is used in R2 and R3,
is to have very accurate network documentation that shows where you have assigned IP network addresses.
Table 7: Routing Table in Router R1 for an Incorrectly Configured Network (Example 2)
Ethernet 0
Serial 0
Serial 1
172.16.32.0/24 (Connected)
192.168.100.4/29 (Connected)
172.16.31.0/24 RIP
192.168.100.8/29 (Connected)
172.16.31.0/24 RIP
IP Addressing: IPv4 Addressing Configuration Guide
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Configuring IPv4 Addresses
Classless Inter-Domain Routing
Figure 6: Incorrectly Configured Network (Example 2)
For a more thorough explanation of IP routing, see the "Related Documents" section for a list of documents
related to IP routing.
Classless Inter-Domain Routing
Due to the continuing increase in internet use and the limitations on how IP addresses can be assigned using
the class structure shown in the table above, a more flexible method for allocating IP addresses was required.
The new method is documented in RFC 1519 Classless Inter-Domain Routing (CIDR): an Address Assignment
and Aggregation Strategy. CIDR allows network administrators to apply arbitrary masks to IP addresses to
create an IP addressing plan that meets the requirements of the networks that they administrate.
For more information on CIDR, refer to RFC 1519 at http://www.ietf.org/rfc/rfc1519.txt.
Prefixes
The term prefix is often used to refer to the number of bits of an IP network address that are of importance
for building routing tables. If you are using only classful (strict adherence to A, B, and C network address
boundaries) IP addresses, the prefixes are the same as the masks for the classes of addresses. For example,
using classful IP addressing, a class C IP network address such as 192.168.10.0 uses a 24-bit mask (/24 or
255.255.255.0) and can also be said to have a 24-bit prefix.
If you are using CIDR, the prefixes are arbitrarily assigned to IP network addresses based on how you want
to populate the routing tables in your network. For example, a group of class C IP addresses such as
192.168.10.0, 192.168.11.0, 192.168.12.0, 192.168.13.0 can be advertised as a single route to 192.168.0.0
with a 16-bit prefix (192.168.0.0/16). This results in a 4:1 reduction in the number of routes that the routers
in your network need to manage.
IP Addressing: IPv4 Addressing Configuration Guide
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Configuring IPv4 Addresses
How to Configure IP Addresses
How to Configure IP Addresses
Establishing IP Connectivity to a Network by Assigning an IP Address to an
Interface
Perform this task to configure an IP address on an interface.
SUMMARY STEPS
1. enable
2. configure terminal
3. interface type number
4. no shutdown
5. ip address ip-address mask
6. end
DETAILED STEPS
Step 1
Command or Action
Purpose
enable
Enables privileged EXEC mode.
Example:
• Enter your password if prompted.
Router> enable
Step 2
configure terminal
Enters global configuration mode.
Example:
Router# configure terminal
Step 3
interface type number
Specifies an interface and enters interface configuration
mode.
Example:
Router(config)# interface fastethernet 0/0
Step 4
no shutdown
Example:
Router(config-if)# no shutdown
IP Addressing: IPv4 Addressing Configuration Guide
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Enables the interface.
Configuring IPv4 Addresses
Increasing the Number of IP Hosts that Are Supported on a Network by Using Secondary IP Addresses
Step 5
Command or Action
Purpose
ip address ip-address mask
Configures the IP address on the interface.
Example:
Router(config-if)# ip address 172.16.16.1
255.255.240.0
Step 6
Exits the current configuration mode and returns to
privileged EXEC mode.
end
Example:
Router(config-if)# end
Troubleshooting Tips
The following commands can help troubleshoot IP addressing:
• show ip interface --Displays the IP parameters for the interface.
• show ip route connected --Displays the IP networks the networking device is connected to.
Increasing the Number of IP Hosts that Are Supported on a Network by Using
Secondary IP Addresses
If you have a situation in which you need to connect more IP hosts to a network segment and you have used
all of the available IP host addresses for the subnet to which you have assigned the segment, you can avoid
having to readdress all of the hosts with a different subnet by adding a second IP network address to the
network segment.
Perform this task to configure a secondary IP address on an interface.
SUMMARY STEPS
1. enable
2. configure terminal
3. interface type number
4. no shutdown
5. ip address ip-address mask
6. ip address ip-address mask secondary
7. end
IP Addressing: IPv4 Addressing Configuration Guide
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Configuring IPv4 Addresses
Increasing the Number of IP Hosts that Are Supported on a Network by Using Secondary IP Addresses
DETAILED STEPS
Step 1
Command or Action
Purpose
enable
Enables privileged EXEC mode.
Example:
• Enter your password if prompted.
Router> enable
Step 2
configure terminal
Enters global configuration mode.
Example:
Router# configure terminal
Step 3
interface type number
Specifies an interface and enters interface
configuration mode.
Example:
Router(config)# interface fastethernet 0/0
Step 4
no shutdown
Enables the interface.
Example:
Router(config-if)# no shutdown
Step 5
ip address ip-address mask
Configures the IP address on the interface.
Example:
Router(config-if)# ip address 172.16.16.1
255.255.240.0
Step 6
ip address ip-address mask secondary
Configures the secondary IP address on the interface.
Example:
Router(config-if)# ip address 172.16.32.1
255.255.240.0 secondary
Step 7
Exits the current configuration mode and returns to
privileged EXEC mode.
end
Example:
Router(config-if)# end
Troubleshooting Tips
The following commands can help troubleshoot IP addressing:
IP Addressing: IPv4 Addressing Configuration Guide
16
Configuring IPv4 Addresses
Maximizing the Number of Available IP Subnets by Allowing the Use of IP Subnet Zero
• show ip interface --Displays the IP parameters for the interface.
• show ip route connected --Displays the IP networks the networking device is connected to.
What to Do Next
If your network has two or more routers and you have already configured a routing protocol, make certain
that the other routers can reach the new IP network that you assigned. You might need to modify the
configuration for the routing protocol on the router so that it advertises the new network. Consult the Cisco
IOS IP Routing: Protocol-Independent Configuration Guide for information on configuring routing protocols.
Maximizing the Number of Available IP Subnets by Allowing the Use of IP
Subnet Zero
If you using subnetting in your network and you are running out of network addresses, you can configure
your networking device to allow the configuration of subnet zero. This adds one more usable network address
for every subnet in your IP addressing scheme. The table above shows the IP subnets (including subnet 0) for
172.16.0.0/20.
Perform this task to enable the use of IP subnet zero on your networking device.
SUMMARY STEPS
1. enable
2. configure terminal
3. ip subnet-zero
4. interface type number
5. no shutdown
6. ip address ip-address mask
7. end
DETAILED STEPS
Step 1
Command or Action
Purpose
enable
Enables privileged EXEC mode.
Example:
• Enter your password if prompted.
Router> enable
Step 2
configure terminal
Enters global configuration mode.
Example:
Router# configure terminal
IP Addressing: IPv4 Addressing Configuration Guide
17
Configuring IPv4 Addresses
Specifying the Format of Network Masks
Step 3
Command or Action
Purpose
ip subnet-zero
Enables the use of IP subnet zero.
Example:
Router(config)# ip subnet-zero
Step 4
interface type number
Specifies an interface and enters interface configuration
mode.
Example:
Router(config)# interface fastethernet 0/0
Step 5
no shutdown
Enables the interface.
Example:
Router(config-if)# no shutdown
Step 6
ip address ip-address mask
Configures the subnet zero IP address on the interface.
Example:
Router(config-if)# ip address 172.16.0.1
255.255.240.0
Step 7
Exits the current configuration mode and returns to
privileged EXEC mode.
end
Example:
Router(config-if)# end
Troubleshooting Tips
The following commands can help troubleshoot IP addressing:
• show ip interface --Displays the IP parameters for the interface.
• show ip route connected --Displays the IP networks the networking device is connected to.
Specifying the Format of Network Masks
By default, show commands display an IP address and then its netmask in dotted decimal notation. For
example, a subnet would be displayed as 131.108.11.55 255.255.255.0.
You might find it more convenient to display the network mask in hexadecimal format or bit count format
instead. The hexadecimal format is commonly used on UNIX systems. The previous example would be
displayed as 131.108.11.55 0XFFFFFF00.
IP Addressing: IPv4 Addressing Configuration Guide
18
Configuring IPv4 Addresses
Specifying the Format of Network Masks
The bit count format for displaying network masks is to append a slash (/) and the total number of bits in the
netmask to the address itself. The previous example would be displayed as 131.108.11.55/24.
Specifying the Format in Which Netmasks Appear for the Current Session
Perform this task to specify the format in which netmasks appear for the current session.
SUMMARY STEPS
1. enable
2. term ip netmask-format {bitcount | decimal | hexadecimal}
DETAILED STEPS
Step 1
Command or Action
Purpose
enable
Enables privileged EXEC mode.
Example:
• Enter your password if prompted.
Router> enable
Step 2
term ip netmask-format {bitcount | decimal |
hexadecimal}
Specifies the format the router uses to display network
masks.
Example:
Router# term ip netmask-format hexadecimal
Specifying the Format in Which Netmasks Appear for an Individual Line
Perform this task to specify the format in which netmasks appear for an individual line.
SUMMARY STEPS
1. enable
2. configure terminal
3. line vty first last
4. term ip netmask-format {bitcount | decimal | hexadecimal}
5. end
DETAILED STEPS
Step 1
Command or Action
Purpose
enable
Enables privileged EXEC mode.
IP Addressing: IPv4 Addressing Configuration Guide
19
Configuring IPv4 Addresses
Using IP Unnumbered Interfaces on Point-to-Point WAN Interfaces to Limit Number of IP Addresses Required
Command or Action
Purpose
• Enter your password if prompted.
Example:
Router> enable
Step 2
configure terminal
Enters global configuration mode.
Example:
Router# configure terminal
Step 3
line vty
first last
Enters line configuration mode for the range of lines
specified by the first and last arguments.
Example:
Router(config)# line vty 0 4
Step 4
term ip netmask-format {bitcount | decimal |
hexadecimal}
Specifies the format the router uses to display the network
mask for an individual line.
Example:
Router(config-line)# ip netmask-format
hexadecimal
Step 5
Exits the current configuration mode and returns to
privileged EXEC mode.
end
Example:
Router(config-if)# end
Using IP Unnumbered Interfaces on Point-to-Point WAN Interfaces to Limit
Number of IP Addresses Required
If you have a limited number of IP network or subnet addresses and you have point-to-point WANs in your
network, you can use the IP Unnumbered Interfaces feature to enable IP connectivity on the point-to-point
WAN interfaces without actually assigning an IP address to them.
Perform this task to configure the IP Unnumbered Interfaces feature on a point-to-point WAN interface.
IP Unnumbered Feature
The IP Unnumbered Interfaces feature enables IP processing on a point-to-point WAN interface without
assigning it an explicit IP address. The IP unnumbered point-to-point WAN interface uses the IP address of
another interface to enable IP connectivity, which conserves network addresses.
IP Addressing: IPv4 Addressing Configuration Guide
20
Configuring IPv4 Addresses
Using IP Unnumbered Interfaces on Point-to-Point WAN Interfaces to Limit Number of IP Addresses Required
Note
The following restrictions apply to the IP Unnumbered Interfaces feature:
• The IP Unnumbered Interfaces feature is only supported on point-to-point (non-multiaccess) WAN
interfaces
• You cannot netboot a Cisco IOS image over an interface that is using the IP Unnumbered Interfaces
feature
SUMMARY STEPS
1. enable
2. configure terminal
3. interface type number
4. no shutdown
5. ip address ip-address mask
6. interface type number
7. no shutdown
8. ip unnumbered type number
9. end
DETAILED STEPS
Step 1
Command or Action
Purpose
enable
Enables privileged EXEC mode.
Example:
• Enter your password if prompted.
Router> enable
Step 2
configure terminal
Enters global configuration mode.
Example:
Router# configure terminal
Step 3
interface type number
Specifies an interface and enters interface configuration
mode.
Example:
Router(config)# interface fastethernet 0/0
Step 4
no shutdown
Enables the interface.
Example:
Router(config-if)# no shutdown
IP Addressing: IPv4 Addressing Configuration Guide
21
Configuring IPv4 Addresses
Using IP addresses with 31-Bit Prefixes on Point-to-Point WAN Interfaces to Limit Number of IP Addresses Required
Step 5
Command or Action
Purpose
ip address ip-address mask
Configures the IP address on the interface.
Example:
Router(config-if)# ip address 172.16.16.1
255.255.240.0
Step 6
interface type number
Specifies a point-to-point WAN interface and enters
interface configuration mode.
Example:
Router(config-if)# interface serial 0/0
Step 7
no shutdown
Enables the point-to-point WAN interface.
Example:
Router(config-if)# no shutdown
Step 8
ip unnumbered type number
Enables the IP unnumbered feature on the point-to-point
WAN interface.
Example:
In this example the point-to-point WAN interface uses IP
address 172.16.16.1 from Fast Ethernet 0/0.
Router(config-if)# ip unnumbered fastethernet
0/0
Step 9
Exits the current configuration mode and returns to
privileged EXEC mode.
end
Example:
Router(config-if)# end
Troubleshooting Tips
The following commands can help troubleshoot IP addressing:
• show ip interface --Displays the IP parameters for the interface.
• show ip route connected --Displays the IP networks the networking device is connected to.
Using IP addresses with 31-Bit Prefixes on Point-to-Point WAN Interfaces to
Limit Number of IP Addresses Required
You can reduce the number of IP subnets used by networking devices to establish IP connectivity to
point-to-point WANs that they are connected to by using IP Addresses with 31-bit Prefixes as defined in RFC
3021.
IP Addressing: IPv4 Addressing Configuration Guide
22
Configuring IPv4 Addresses
Using IP addresses with 31-Bit Prefixes on Point-to-Point WAN Interfaces to Limit Number of IP Addresses Required
Perform this task to configure an IP address with a 31-bit prefix on a point-to-point WAN interface.
RFC 3021
Prior to RFC 3021, Using 31-bit Prefixes on IPv4 Point-to-Point Links , many network administrators assigned
IP address with a 30-bit subnet mask (255.255.255.252) to point-to-point interfaces to conserve IP address
space. Although this practice does conserve IP address space compared to assigning IP addresses with shorter
subnet masks such as 255.255.255.240, IP addresses with a 30-bit subnet mask still require four addresses
per link: two host addresses (one for each host interface on the link), one all-zeros network address, and one
all-ones broadcast network address.
The table below shows an example of the four IP addresses that are created when a 30-bit (otherwise known
as 255.255.255.252 or /30) subnet mask is applied to the IP address 192.168.100.4. The bits that are used to
specify the host IP addresses in bold.
Table 8: Four IP Addresses Created When a 30-Bit Subnet Mask (/30) Is Used
Address
Description
Binary
192.168.100.4/30
All-zeros IP address
11000000.10101000.01100100.00000100
192.168.100.5/30
First host addresses
11000000.10101000.01100100.00000101
192.168.100.6/30
Second host address
11000000.10101000.01100100.00000110
192.168.100.7/30
All-ones broadcast address
11000000.10101000.01100100.00000111
Point-to-point links only have two endpoints (hosts) and do not require broadcast support because any packet
that is transmitted by one host is always received by the other host. Therefore the all-ones broadcast IP address
is not required for a point-to-point interface.
The simplest way to explain RFC 3021 is to say that the use of a 31-bit prefix (created by applying a 31-bit
subnet mask to an IP address) allows the all-zeros and all-ones IP addresses to be assigned as host addresses
on point-to-point networks. Prior to RFC 3021 the longest prefix in common use on point-to-point links was
30-bits, which meant that the all-zeros and all-ones IP addresses were wasted.
The table below shows an example of the two IP addresses that are created when a 31-bit (otherwise known
as 255.255.255.254 or /31) subnet mask is applied to the IP address 192.168.100.4. The bit that is used to
specify the host IP addresses in bold
Table 9: Two IP Addresses Created When a 31-Bit Subnet Mask (/31) Is Used
Address
Description
Binary
192.168.100.4/31
First host address
11000000.10101000.01100100.00000100
192.168.100.5/31
Second host address
11000000.10101000.01100100.00000101
The complete text for RFC 3021 is available at http://www.ietf.org/rfc/rfc3021.txt .
IP Addressing: IPv4 Addressing Configuration Guide
23
Configuring IPv4 Addresses
Using IP addresses with 31-Bit Prefixes on Point-to-Point WAN Interfaces to Limit Number of IP Addresses Required
Before You Begin
You must have classless IP addressing configured on your networking device before you configure an IP
address with a 31-bit prefix on a point-to-point interface. Classless IP addressing is enabled by default in
many versions of Cisco IOS software. If you are not certain that your networking device has IP classless
addressing configured, enter the ip classless command in global configuration mode to enable it.
This task can only be performed on point-to-point (nonmultiaccess) WAN interfaces.
Note
SUMMARY STEPS
1. enable
2. configure terminal
3. ip classless
4. interface type number
5. no shutdown
6. ip address ip-address mask
7. end
DETAILED STEPS
Step 1
Command or Action
Purpose
enable
Enables privileged EXEC mode.
Example:
• Enter your password if prompted.
Router> enable
Step 2
configure terminal
Enters global configuration mode.
Example:
Router# configure terminal
Step 3
ip classless
(Optional) Enables IP classless (CIDR).
Note
Example:
Router(config)# ip classless
IP Addressing: IPv4 Addressing Configuration Guide
24
This command is enabled by default in many versions of
Cisco IOS. If you are not certain if it is enabled by default
in the version of Cisco IOS that your networking device is
running, enter the ip classlesscommand as shown. When
you are done with this task view the configuration. If the
ip classless command does not appear in your configuration,
it is enabled by default.
Configuring IPv4 Addresses
Configuration Examples for IP Addresses
Step 4
Command or Action
Purpose
interface type number
Specifies a point-to-point WAN interface and enters interface
configuration mode.
Example:
Router(config)# interface serial 0/0
Step 5
no shutdown
Enables the interface.
Example:
Router(config-if)# no shutdown
Step 6
ip address ip-address mask
Configures the 31bit prefix IP address on the point-to-point WAN
interface.
Example:
Router(config-if)# ip address
192.168.100.4 255.255.255.254
Step 7
Exits the current configuration mode and returns to privileged EXEC
mode.
end
Example:
Router(config-if)# end
Troubleshooting Tips
The following commands can help troubleshoot IP addressing:
• show ip interface --Displays the IP parameters for the interface.
• show ip route connected --Displays the IP networks the networking device is connected to.
Configuration Examples for IP Addresses
Example Establishing IP Connectivity to a Network by Assigning an IP Address
to an Interface
The following example configures an IP address on three interfaces:
!
interface FastEthernet0/0
no shutdown
ip address 172.16.16.1 255.255.240.0
!
interface FastEthernet0/1
IP Addressing: IPv4 Addressing Configuration Guide
25
Configuring IPv4 Addresses
Example Increasing the Number of IP Hosts that are Supported on a Network by Using Secondary IP Addresses
no shutdown
ip address 172.16.32.1 255.255.240.0
!
interface FastEthernet0/2
no shutdown
ip address 172.16.48.1 255.255.240.0
!
Example Increasing the Number of IP Hosts that are Supported on a Network
by Using Secondary IP Addresses
The following example configures secondary IP addresses on three interfaces:
!
interface FastEthernet0/0
no shutdown
ip address 172.16.16.1 255.255.240.0
ip address 172.16.32.1 255.255.240.0 secondary
!
!
interface FastEthernet0/1
no shutdown
ip address 172.17.16.1 255.255.240.0
ip address 172.17.32.1 255.255.240.0 secondary
!
!
interface FastEthernet0/2
no shutdown
ip address 172.18.16.1 255.255.240.0
ip address 172.18.32.1 255.255.240.0 secondary
!
Example Using IP Unnumbered Interfaces on Point-to-Point WAN Interfaces
to Limit Number of IP Addresses Required
The following example configures the unnumbered IP feature on three interfaces:
!
interface FastEthernet0/0
no shutdown
ip address 172.16.16.1 255.255.240.0
!
interface serial0/0
no shutdown
ip unnumbered fastethernet0/0
!
interface serial0/1
no shutdown
ip unnumbered fastethernet0/0
!
interface serial0/2
no shutdown
ip unnumbered fastethernet0/0
!
IP Addressing: IPv4 Addressing Configuration Guide
26
Configuring IPv4 Addresses
Example Using IP addresses with 31-Bit Prefixes on Point-to-Point WAN Interfaces to Limit Number of IP Addresses
Required
Example Using IP addresses with 31-Bit Prefixes on Point-to-Point WAN
Interfaces to Limit Number of IP Addresses Required
The following example configures 31-bit prefixes on two interfaces:
!
ip classless
!
interface serial0/0
no shutdown
ip address 192.168.100.2 255.255.255.254
!
!
interface serial0/1
no shutdown
ip address 192.168.100.4 255.255.255.254
Example Maximizing the Number of Available IP Subnets by Allowing the Use
of IP Subnet Zero
The following example enables subnet zero:
!
interface FastEthernet0/0
no shutdown
ip address 172.16.16.1 255.255.240.0
!
ip subnet-zero
!
Where to Go Next
If your network has two or more routers and you have not already configured a routing protocol, consult the
Cisco IOS IP Routing Protocols Configuration Guide, Release 12.4T, for information on configuring routing
protocols.
Additional References
Related Documents
Related Topic
Document Title
Cisco IOS commands
Cisco IOS Master Commands List, All Releases
IP addressing commands: complete command syntax, Cisco IOS IP Addressing Services Command
command mode, command history, defaults, usage Reference
guidelines, and examples
IP Addressing: IPv4 Addressing Configuration Guide
27
Configuring IPv4 Addresses
Additional References
Related Topic
Document Title
Fundamental principles of IP addressing and IP
routing
IP Routing Primer ISBN 1578701082
Standards
Standard
Title
No new or modified standards are supported, and
-support for existing standards has not been modified
MIBs
MIB
MIBs Link
No new or modified MIBs are supported, and support To locate and download MIBs for selected platforms,
for existing MIBs has not been modified
Cisco software releases, and feature sets, use Cisco
MIB Locator found at the following URL:
http://www.cisco.com/go/mibs
RFCs
RFC
6
RFC 791
Title
Internet Protocol
http://www.ietf.org/rfc/rfc0791.txt
RFC 1338
Classless Inter-Domain Routing (CIDR): an Address
Assignment and Aggregation Strategy http://
www.ietf.org/rfc/rfc1519.txt
RFC 1466
Guidelines for Management of IP Address Space
http://www.ietf.org/rfc/rfc1466.txt
RFC 1716
Towards Requirements for IP Routers http://
www.ietf.org/rfc/rfc1716.txt
RFC 1918
Address Allocation for Private Internets http://
www.ietf.org/rfc/rfc1918.txt
RFC 3330
Special-Use IP Addresses http://www.ietf.org/rfc/
rfc3330.txt
IP Addressing: IPv4 Addressing Configuration Guide
28
Configuring IPv4 Addresses
Feature Information for IP Addresses
6 These references are only a sample of the many RFCs available on subjects related to IP addressing and IP routing. Refer to the IETF RFC site at
http://www.ietf.org/rfc.html for a full list of RFCs.
Technical Assistance
Description
Link
The Cisco Support and Documentation website
http://www.cisco.com/cisco/web/support/index.htmll
provides online resources to download documentation,
software, and tools. Use these resources to install and
configure the software and to troubleshoot and resolve
technical issues with Cisco products and technologies.
Access to most tools on the Cisco Support and
Documentation website requires a Cisco.com user ID
and password.
Feature Information for IP Addresses
The following table provides release information about the feature or features described in this module. This
table lists only the software release that introduced support for a given feature in a given software release
train. Unless noted otherwise, subsequent releases of that software release train also support that feature.
Use Cisco Feature Navigator to find information about platform support and Cisco software image support.
To access Cisco Feature Navigator, go to . An account on Cisco.com is not required.
Table 10: Feature Information for IP Addresses
Feature Name
Releases
Feature Information
Classless Inter-Domain Routing
10.0
CIDR is a new way of looking at
IP addresses that eliminates the
concept of classes (class A, class
B, and so on). For example,
network 192.213.0.0, which is an
illegal class C network number, is
a legal supernet when it is
represented in CIDR notation as
192.213.0.0/16. The /16 indicates
that the subnet mask consists of 16
bits (counting from the left).
Therefore, 192.213.0.0/16 is
similar to 192.213.0.0 255.255.0.0.
The following command was
introduced or modified: ip
classless.
IP Addressing: IPv4 Addressing Configuration Guide
29
Configuring IPv4 Addresses
Feature Information for IP Addresses
Feature Name
Releases
Feature Information
IP Subnet Zero
10.0
In order to conserve IP address
space IP Subnet Zero allows the
use of the all-zeros subnet as an IP
address on an interface, such as
configuring 172.16.0.1/24 on Fast
Ethernet 0/0.
The following command was
introduced or modified: ip
subnet-zero.
IP Unnumbered Interfaces
10.0
In order to conserve IP address
space, IP unnumbered interfaces
use the IP address of another
interface to enable IP connectivity.
The following command was
introduced or modified: ip
unnumbered.
Using 31-bit Prefixes on IP
Point-to-Point Links
IP Addressing: IPv4 Addressing Configuration Guide
30
12.0(14)S 12.2(4)T
In order to conserve IP address
space on the Internet, a 31-bit
prefix length allows the use of only
two IP addresses on a
point-to-point link. Previously,
customers had to use four IP
addresses or unnumbered interfaces
for point-to-point links.
CHAPTER
3
IP Overlapping Address Pools
The IP Overlapping Address Pools feature improves flexibility in assigning IP addresses dynamically. This
feature allows you to configure overlapping IP address pool groups to create different address spaces and
concurrently use the same IP addresses in different address spaces.
• Finding Feature Information, page 31
• Restrictions for IP Overlapping Address Pools, page 31
• Information About IP Overlapping Address Pools, page 32
• How to Configure IP Overlapping Address Pools, page 32
• Configuration Examples for Configuring IP Overlapping Address Pools, page 33
• Additional References, page 34
• Feature Information for Configuring IP Overlapping Address Pools, page 35
• Glossary, page 36
Finding Feature Information
Your software release may not support all the features documented in this module. For the latest caveats and
feature information, see Bug Search Tool and the release notes for your platform and software release. To
find information about the features documented in this module, and to see a list of the releases in which each
feature is supported, see the feature information table.
Use Cisco Feature Navigator to find information about platform support and Cisco software image support.
To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.
Restrictions for IP Overlapping Address Pools
The Cisco IOS XE software checks for duplicate addresses on a per-group basis. The check for duplicate
addresses means that you can configure pools in multiple groups that could have possible duplicate addresses.
The IP Overlapping Address Pools feature should be used only in cases where overlapping IP address pools
make sense, such as Multiprotocol Label Switching (MPLS) Virtual Private Network (VPN) environments
where multiple IP address spaces are supported.
IP Addressing: IPv4 Addressing Configuration Guide
31
IP Overlapping Address Pools
Information About IP Overlapping Address Pools
Information About IP Overlapping Address Pools
Benefits
The IP Overlapping Address Pools gives greater flexibility in assigning IP addresses dynamically. It allows
you to configure overlapping IP address pool groups to create different address spaces and concurrently use
the same IP addresses in different address spaces.
How IP Address Groups Work
IP Control Protocol (IPCP) IP pool processing implements all IP addresses as belonging to a single IP address
space, and a given IP address should not be assigned multiple times. IP developments such as virtual private
dialup network (VPDN) and Network Address Translation (NAT) implement the concept of multiple IP
address spaces where it can be meaningful to reuse IP addresses, although such usage must ensure that these
duplicate address are not placed in the same IP address space. An IP address group to support multiple IP
address spaces and still allow the verification of nonoverlapping IP address pools within a pool group. Pool
names must be unique within the router. The pool name carries an implicit group identifier because that pool
name can be associated only with one group. Pools without an explicit group name are considered members
of the base system group and are processed in the same manner as the original IP pool implementation.
Existing configurations are not affected by the new pool feature. The “group” concept is an extension of the
existing ip local pool command. Processing of pools that are not specified as a member of a group is unchanged
from the existing implementation.
How to Configure IP Overlapping Address Pools
Configuring and Verifying a Local Pool Group
Perform this task to configure a local pool group and verify that it exists.
SUMMARY STEPS
1. enable
2. configure terminal
3. ip local pool {default | poolname} {low-ip-address [high-ip-address] [group group-name] [cache-size
size]}
4. show ip local pool [poolname | [group group-name]]
DETAILED STEPS
Step 1
Command or Action
Purpose
enable
Enables privileged EXEC mode.
IP Addressing: IPv4 Addressing Configuration Guide
32
IP Overlapping Address Pools
Configuration Examples for Configuring IP Overlapping Address Pools
Command or Action
Purpose
• Enter your password if prompted.
Example:
Router> enable
Step 2
Enters global configuration mode.
configure terminal
Example:
Router# configure terminal
Step 3
ip local pool {default | poolname} {low-ip-address
[high-ip-address] [group group-name] [cache-size size]}
Configures a group of local IP address pools, gives
this group a name, and specifies a cache size.
Example:
Router(config)# ip local pool testpool 10.2.2.1
10.2.2.10 group testgroup cache-size 10000
Step 4
show ip local pool [poolname | [group group-name]]
Displays statistics for any defined IP address pools.
Example:
Router(config)# show ip local pool group testgroup
testpool
Configuration Examples for Configuring IP Overlapping Address
Pools
Define Local Address Pooling as the Global Default Mechanism Example
The following example shows how to configure local pooling as the global default mechanism:
ip address-pool local
ip local pool default 192.168.15.15 192.168.15.16
Configure Multiple Ranges of IP Addresses into One Pool Example
The following example shows how to configure two ranges of IP addresses for one IP address pool:
ip local pool default 192.169.10.10 192.169.10.20
ip local pool default 192.168.50.25 192.168.50.50
IP Addressing: IPv4 Addressing Configuration Guide
33
IP Overlapping Address Pools
Additional References
Additional References
The following sections provide references related to configuring IP Overlapping Address Pools.
Related Documents
Related Topic
Document Title
Dial commands: complete command syntax,
command mode, command history, defaults, usage
guidelines, and examples
Cisco IOS Dial Services Command Reference
IP address pooling
“Configuring Media-Independent PPP and Multilink
PPP” chapter of the Cisco IOS XE Dial Technologies
Configuration Guide
Standards
Standards
Title
No new or modified standards are supported by this -feature, and support for existing standards has not
been modified by this feature.
MIBs
MIBs
MIBs Link
No new or modified MIBs are supported by this
feature, and support for existing MIBs has not been
modified by this feature.
To locate and download MIBs for selected platforms,
Cisco IOS XE releases, and feature sets, use Cisco
MIB Locator found at the following URL:
http://www.cisco.com/go/mibs
RFCs
RFCs
Title
RFC 826
Address Resolution Protocol
RFC 903
Reverse Address Resolution Protocol
RFC 1027
Proxy Address Resolution Protocol
RFC 1042
Standard for the Transmission of IP Datagrams over
IEEE 802 Networks
IP Addressing: IPv4 Addressing Configuration Guide
34
IP Overlapping Address Pools
Feature Information for Configuring IP Overlapping Address Pools
Technical Assistance
Description
Link
The Cisco Support website provides extensive online http://www.cisco.com/techsupport
resources, including documentation and tools for
troubleshooting and resolving technical issues with
Cisco products and technologies.
To receive security and technical information about
your products, you can subscribe to various services,
such as the Product Alert Tool (accessed from Field
Notices), the Cisco Technical Services Newsletter,
and Really Simple Syndication (RSS) Feeds.
Access to most tools on the Cisco Support website
requires a Cisco.com user ID and password.
Feature Information for Configuring IP Overlapping Address
Pools
The following table provides release information about the feature or features described in this module. This
table lists only the software release that introduced support for a given feature in a given software release
train. Unless noted otherwise, subsequent releases of that software release train also support that feature.
Use Cisco Feature Navigator to find information about platform support and Cisco software image support.
To access Cisco Feature Navigator, go to . An account on Cisco.com is not required.
Table 11: Feature Information for Configuring IP Overlapping Address Pools
Feature Name
Releases
Feature Information
IP Overlapping Address Pools
Cisco IOS XE Release 2.1
The IP Overlapping Address Pools
feature improves flexibility in
assigning IP addresses
dynamically. This feature allows
you to configure overlapping IP
address pool groups to create
different address spaces and
concurrently use the same IP
addresses in different address
spaces.
The following commands were
modified by this feature:ip local
pooland show ip local pool.
IP Addressing: IPv4 Addressing Configuration Guide
35
IP Overlapping Address Pools
Glossary
Glossary
IPCP --IP Control Protocol. Protocol that establishes and configures IP over PPP.
MPLS --Multiprotocol Label Switching. Switching method that forwards IP traffic using a label. This label
instructs the routers and the switches in the network where to forward the packets based on preestablished IP
routing information.
NAT --Network Address Translation. Mechanism for reducing the need for globally unique IP addresses.
NAT allows an organization with addresses that are not globally unique to connect to the Internet by translating
those addresses into globally routable address space. Also known as Network Address Translator.
VPDN --virtual private dialup network. Also known as virtual private dial network. A VPDN is a network
that extends remote access to a private network using a shared infrastructure. VPDNs use Layer 2 tunnel
technologies (L2F, L2TP, and PPTP) to extend the Layer 2 and higher parts of the network connection from
a remote user across an ISP network to a private network. VPDNs are a cost-effective method of establishing
a long distance, point-to-point connection between remote dial users and a private network. See also VPN.
VPN --Virtual Private Network. Enables IP traffic to travel securely over a public TCP/IP network by encrypting
all traffic from one network to another. A VPN uses “tunneling” to encrypt all information at the IP level.
VRF --A VPN routing and forwarding instance. A VRF consists of an IP routing table, a derived forwarding
table, a set of interfaces that use the forwarding table, and a set of rules and routing protocols that determine
what goes into the forwarding table. In general, a VRF includes the routing information that defines a customer
VPN site that is attached to a PE router.
IP Addressing: IPv4 Addressing Configuration Guide
36
CHAPTER
4
IP Unnumbered Ethernet Polling Support
The IP Unnumbered Ethernet Polling Support feature provides IP unnumbered support for Ethernet physical
interfaces. This support already exists for serial interfaces.
• Finding Feature Information, page 37
• Information About IP Unnumbered Ethernet Polling Support, page 37
• How to Configure IP Unnumbered Ethernet Polling Support, page 38
• Configuration Examples for IP Unnumbered Ethernet Polling Support, page 42
• Additional References, page 42
• Feature Information for IP Unnumbered Ethernet Polling Support, page 43
Finding Feature Information
Your software release may not support all the features documented in this module. For the latest caveats and
feature information, see Bug Search Tool and the release notes for your platform and software release. To
find information about the features documented in this module, and to see a list of the releases in which each
feature is supported, see the feature information table.
Use Cisco Feature Navigator to find information about platform support and Cisco software image support.
To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.
Information About IP Unnumbered Ethernet Polling Support
IP Unnumbered Ethernet Polling Support Overview
IP unnumbered support for serial interfaces is extended to Ethernet physical interfaces. Unnumbered Ethernet
physical interfaces are used in the same manner as unnumbered serial interfaces. On a device, if a loopback
interface is configured and an IP address is assigned to it, using the polling option more than one Ethernet
physical interface can be unnumbered to the loopback.
IP Addressing: IPv4 Addressing Configuration Guide
37
IP Unnumbered Ethernet Polling Support
How to Configure IP Unnumbered Ethernet Polling Support
The polling option enables the dynamic discovery of hosts (connected though the unnumbered interfaces)
based on the Address Resolution Protocol (ARP) protocol.
How to Configure IP Unnumbered Ethernet Polling Support
Enabling Polling on an Ethernet Interface
SUMMARY STEPS
1. enable
2. configure terminal
3. interface type number
4. ip address ip-address mask
5. exit
6. interface type number
7. ip unnumbered type number poll
8. end
DETAILED STEPS
Step 1
Command or Action
Purpose
enable
Enables privileged EXEC mode.
Example:
• Enter your password if prompted.
Device> enable
Step 2
configure terminal
Enters global configuration mode.
Example:
Device# configure terminal
Step 3
interface type number
Specifies an interface and enters interface configuration
mode.
Example:
Device(config)# interface loopback 0
Step 4
ip address ip-address mask
Example:
Device(config-if)# ip address 209.165.200.229
255.255.240.224
IP Addressing: IPv4 Addressing Configuration Guide
38
Configures the IP address on the interface.
IP Unnumbered Ethernet Polling Support
Configuring the Queue Size and the Packet Rate for IP ARP Polling for Unnumbered Interfaces
Step 5
Command or Action
Purpose
exit
Exits interface configuration mode and returns to global
configuration mode.
Example:
Device(config-if)# exit
Step 6
interface type number
Specifies an interface and enters interface configuration
mode.
Example:
Device(config)# interface ethernet 0/0
Step 7
ip unnumbered type number poll
Enables IP–connected host polling on the specified
interface.
Example:
Device(config-if)# ip unnumbered loopback 0 poll
Step 8
Returns to privileged EXEC mode.
end
Example:
Device(config-if)# end
Configuring the Queue Size and the Packet Rate for IP ARP Polling for
Unnumbered Interfaces
SUMMARY STEPS
1. enable
2. configure terminal
3. ip arp poll queue queue-size
4. ip arp poll rate packet-rate
5. end
DETAILED STEPS
Step 1
Command or Action
Purpose
enable
Enables privileged EXEC mode.
Example:
• Enter your password if prompted.
Device> enable
IP Addressing: IPv4 Addressing Configuration Guide
39
IP Unnumbered Ethernet Polling Support
Verifying IP Unnumbered Ethernet Polling Support
Step 2
Command or Action
Purpose
configure terminal
Enters global configuration mode.
Example:
Device# configure terminal
Step 3
ip arp poll queue queue-size
Configures the IP ARP polling queue size.
Example:
Device(config)# ip arp poll queue 1000
Step 4
ip arp poll rate packet-rate
Configures the IP ARP polling packet rate, in packets
per second.
Example:
Device(config)# ip arp poll rate 1000
Step 5
end
Returns to privileged EXEC mode.
Example:
Device(config-if)# end
Verifying IP Unnumbered Ethernet Polling Support
Perform this task to verify IP unnumbered Ethernet polling support.
Note
The show commands are not in any specific order.
SUMMARY STEPS
1. enable
2. show ip arp poll
3. show ip interface type number unnumbered
4. show ip interface type number unnumbered detail
DETAILED STEPS
Step 1
enable
Enables privileged EXEC mode.
IP Addressing: IPv4 Addressing Configuration Guide
40
IP Unnumbered Ethernet Polling Support
Verifying IP Unnumbered Ethernet Polling Support
Example:
Device> enable
Step 2
show ip arp poll
Displays the IP ARP host polling status.
Example:
Device# show ip arp poll
Number of IP addresses processed for polling: 438
Number of entries in the queue: 100 (high water mark: 154, max: 1000)
Number of request dropped:
Queue was full: 1288
Request was throttled by incomplete ARP: 10
Duplicate entry found in queue: 1431
Step 3
show ip interface type number unnumbered
Displays the status of unnumbered interface support on interfaces configured for IP.
Example:
Device# show ip interface loopback 0 unnumbered
Number of unnumbered interfaces with polling: 10
Number of IP addresses processed for polling: 15
Number of IP addresses in queue for polling: 4
Step 4
show ip interface type number unnumbered detail
Displays the detailed status of unnumbered interface support on interfaces configured for IP.
Example:
Device# show ip interface loopback 0 unnumbered detail
Number of unnumbered interfaces with polling: 10
Number of IP addresses processed for polling: 15
Last 10 IP addresses processed for polling:
209.165.201.2
209.165.201.3
209.165.201.4
209.165.201.5
209.165.201.6
209.165.201.7
209.165.201.8
209.165.201.9
209.165.201.10
209.165.201.11
Number of IP addresses in queue for polling: 4 (high water mark: 5)
209.165.201.12
209.165.201.13
209.165.201.14
209.165.201.15
IP Addressing: IPv4 Addressing Configuration Guide
41
IP Unnumbered Ethernet Polling Support
Configuration Examples for IP Unnumbered Ethernet Polling Support
Configuration Examples for IP Unnumbered Ethernet Polling
Support
Example: Enabling Polling on an Ethernet Interface
Device> enable
Device# configure terminal
Device(config)# interface loopback 0
Device(config-if)# ip address 209.165.200.229 255.255.240.224
Device(config-if)# exit
Device(config)# interface ethernet 0/0
Device(config-if)# ip unnumbered loopback 0 poll
Device(config-if)# end
Example: Configuring the Queue Size and the Packet Rate for IP ARP Polling
for Unnumbered Interfaces
Device> enable
Device# configure terminal
Device(config)# ip arp poll queue 1000
Device(config)# ip arp poll rate 1000
Device(config)# end
Additional References
Related Documents
Related Topic
Document Title
Cisco IOS commands
Cisco IOS Master Command List,
All Releases
IPv4 Addressing commands
Cisco IOS IP Addressing Services
Command Reference
Conceptual information about IPv4 addresses
“Configuring IPv4 Addresses”
module in the IP Addressing:
IPv4 Addressing Configuration
Guide
IP Addressing: IPv4 Addressing Configuration Guide
42
IP Unnumbered Ethernet Polling Support
Feature Information for IP Unnumbered Ethernet Polling Support
Technical Assistance
Description
Link
The Cisco Support and Documentation website
http://www.cisco.com/cisco/web/support/index.html
provides online resources to download documentation,
software, and tools. Use these resources to install and
configure the software and to troubleshoot and resolve
technical issues with Cisco products and technologies.
Access to most tools on the Cisco Support and
Documentation website requires a Cisco.com user ID
and password.
Feature Information for IP Unnumbered Ethernet Polling Support
The following table provides release information about the feature or features described in this module. This
table lists only the software release that introduced support for a given feature in a given software release
train. Unless noted otherwise, subsequent releases of that software release train also support that feature.
Use Cisco Feature Navigator to find information about platform support and Cisco software image support.
To access Cisco Feature Navigator, go to . An account on Cisco.com is not required.
Table 12: Feature Information for IP Unnumbered Ethernet Polling Support
Feature Name
Releases
Feature Information
IP Unnumbered Ethernet Polling
Support
Cisco IOS XE Release 3.8S
The IP Unnumbered Ethernet
Polling Support feature provides
IP unnumbered support for
Ethernet physical interfaces.
The following commands were
introduced or modified: clear ip
arp poll statistics, clear ip
interface, ip arp poll, ip
unnumbered poll, show ip arp
poll, and show ip interface
unnumbered.
IP Addressing: IPv4 Addressing Configuration Guide
43
IP Unnumbered Ethernet Polling Support
Feature Information for IP Unnumbered Ethernet Polling Support
IP Addressing: IPv4 Addressing Configuration Guide
44
CHAPTER
5
Auto-IP
The auto-IP feature automatically provides IP addresses to the nodes inserted into a ring. In ring topology,
when a device is inserted into the ring, the neighboring node interfaces require manual reconfiguration. The
auto-IP feature addresses the problem of manually reconfiguring nodes during insertion, deletion, and
movement of nodes within the ring. The auto-IP feature is supported on the following:
• Ethernet interfaces and sub interfaces.
• Virtual routing and forwarding instance (VRF) interfaces.
• Switch Virtual Interfaces (SVIs).
• EtherChannels.
Attention
Note
To know the release versions that support the auto-IP feature on VRF interfaces, SVIs, and EtherChannels,
refer Feature Information for Auto-IP.
When a device is inserted into a ring, it is called a node.
• Finding Feature Information, page 46
• Prerequisites for Auto-IP, page 46
• Restrictions for Auto-IP, page 46
• Information About Auto-IP, page 47
• How to Configure Auto-IP, page 54
• Configuration Examples for Auto-IP, page 61
• Additional References for Auto-IP, page 62
• Feature Information for Auto-IP, page 63
IP Addressing: IPv4 Addressing Configuration Guide
45
Auto-IP
Finding Feature Information
Finding Feature Information
Your software release may not support all the features documented in this module. For the latest caveats and
feature information, see Bug Search Tool and the release notes for your platform and software release. To
find information about the features documented in this module, and to see a list of the releases in which each
feature is supported, see the feature information table at the end of this module.
Use Cisco Feature Navigator to find information about platform support and Cisco software image support.
To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.
Prerequisites for Auto-IP
• Link Layer Discovery Protocol (LLDP) must be enabled on the device before the auto-IP functionality
is enabled on the node interface.
Auto-IP on an EtherChannel
• When you configure auto-IP on an EtherChannel, ensure that LLDP is enabled on the member interfaces
of the EtherChannel.
• Auto-IP configuration on an interface must be removed before moving an interface into an EtherChannel.
Auto-IP on VRF interfaces
• If you intend to configure auto-IP on an interface for a specific virtual routing and forwarding instance
(VRF), then ensure that the interface is presently within the VRF. If you enable auto-IP on an interface
and then associate the interface to a VRF, the auto-IP settings on the interface will be cleared, and you
will have to enable the auto-IP feature on the VRF interface again.
Restrictions for Auto-IP
• Auto-IP addresses must not contain an even number in the last octet (such as 10.1.1.2, where the number
in the last octet is 2).
Auto-IP on VRF interfaces
• Auto-IP configuration on an interface is not retained when the interface is moved from one virtual routing
and forwarding instance (VRF) to another, including the global VRF.
• Interface nodes in different VRFs cannot be configured for the same ring. Ensure that the nodes you
select belong to the same VRF.
• If a VRF address family is IPv6, you cannot configure auto-IP on the interfaces within the VRF. You
can configure auto-IP on a VRF interface if the VRF address family is IPv4.
Auto-IP on SVI interfaces
• Auto-IP configuration is not possible on a Switch Virtual Interface (SVI) with more than one physical
interface. The SVI physical interface must be an access port or trunk port with only one associated
VLAN or a bridge domain interface (BDI).
IP Addressing: IPv4 Addressing Configuration Guide
46
Auto-IP
Information About Auto-IP
Auto-IP on EtherChannel interfaces
• Auto-IP configuration can be done on an EtherChannel interface, but not on a member interface of the
EtherChannel.
Information About Auto-IP
Auto-IP Overview
The auto-IP feature is an enhancement of Link Layer Discovery Protocol (LLDP). LLDP uses a set of attributes
to discover neighbor devices. This attribute set is called Type Length Value (TLV) as it contains type, length,
and value descriptions.
In a ring topology, two network-to-network interfaces (NNIs or node interfaces) of a device are used to be
part of the ring. For a ring to function as an auto-IP ring, you must configure the auto-IP feature on all the
node interfaces within the ring. One node interface of a device is designated as the owner-interface and the
other interface as the non-owner-interface. In an auto-IP ring, the owner-interface of a device is connected to
a non-owner-interface of the neighbor device. A sample topology is given below:
When a new device is inserted into an auto-IP ring, owner and non-owner-interfaces of the inserted device
are identified. The node interface of the inserted device that is connected to an owner-interface is designated
as the non-owner-interface, and it automatically receives an IP address from the connected neighbor device.
The IP address is automatically configured on the interface. Since the non-owner-interface is identified, the
other node interface of the inserted device is designated as the owner-interface, and the device assigns a pre
configured auto-IP address to its designated owner-interface.
An auto-IP address is a preconfigured address configured on a node interface to make the interface capable
of automatically assigning an IP address to a new neighbor interface that is detected in the auto-IP ring. The
configured auto-IP address is used for allocation purposes.
You must configure the same auto-IP address on the two node interfaces that are designated to be part of an
auto-IP ring, and the auto-IP address must contain an odd number in the last octet. The auto-IP address is
assigned to the owner-interface when the device is introduced into an auto-IP ring. Since each auto-IP address
contains an odd number in the last octet, the IP address derived by subtracting 1 from the last octet is an even
number, and is not used for designating auto-IP addresses. This IP address is allocated to a newly detected
neighbor, non-owner-interface.
For example, if we assume that the device R3 is inserted between the devices R1 and R2 in the above topology,
and the auto-IP address 10.1.1.3 is configured on e0/1 and e0/0, the two node interfaces on device R3, then
R1 assigns an IP address to the non-owner-interface of R3, e0/1. The IP address 10.1.1.3 is assigned to the
IP Addressing: IPv4 Addressing Configuration Guide
47
Auto-IP
Auto-IP Overview
owner-interface of R3, e0/0. The IP address derived by subtracting 1 from the last octet of the auto-IP address
is 10.1.1.2. 10.1.1.2 is assigned to the neighbor non-owner-interface of the connected neighbor device R2.
Auto-IP TLV exchange
Before insertion, the node interfaces are not designated as owner and non-owner. After insertion, the auto-IP
TLV is exchanged between the neighbor devices. During this initial negotiation with the adjacent device
interfaces, owner and non-owner-interfaces are determined automatically.
After a device is inserted into a ring, the auto-IP address configured for the device (such as 10.1.1.3) is assigned
to the owner-interface for the /31 subnet. An owner-interface has a priority 2 in the auto-IP TLV, and a
non-owner-interface has priority 0 in the auto-IP TLV. If there is no assigned IP address on the node interface
(before the node is inserted into a ring), then the ring interface has priority 1 in the auto-IP TLV.
The IP address negotiation is based on priority; the higher value of priority wins the negotiation. If the priority
is equal, then IP negotiation fails. This scenario usually occurs when there is an incorrect configuration or
wiring. In such a scenario, you must ensure that the configuration and wiring is proper.
Auto-IP on VRF interfaces
Some points on auto-IP configuration on virtual routing and forwarding instance (VRF) interfaces are noted
below:
• Auto-IP configuration on an interface is removed when the interface is moved from one VRF to another,
including the global VRF. So, assign the interface to a VRF and then configure the auto-IP feature on
the interface.
• You can configure auto-IP on a VRF interface only if the address family of the VRF is IPv4. If the IPv4
address family configuration is removed from a VRF, the auto-IP configuration is removed from all the
interfaces within the VRF.
• If a VRF address family is IPv6, you cannot configure auto-IP on the interfaces within the VRF. However,
if a VRF address family is IPv4 and IPv6, you can configure auto-IP on the interfaces within the VRF.
• If the IPv6 address family configuration is removed from a VRF with both IPv4 and IPv6 address-family
configuration, the auto-IP configuration on the interfaces within the VRF remain intact.
• If a VRF is deleted, then the auto-IP configuration on all the interfaces assigned to the VRF are removed.
• A specific ring has two interface nodes. Ensure that the two nodes you select belong to the same VRF.
Nodes in different VRFs cannot be configured for the same ring.
• Within a VRF, the same auto-IP address cannot be used for different ring IDs.
Auto-IP on EtherChannel interfaces
Some points on auto-IP configuration for an EtherChannel interface are noted below:
• You can configure auto-IP on an EtherChannel interface. If you configure the auto-IP feature on an
EtherChannel and then add member interfaces to the EtherChannel, then auto-IP TLV information is
carried to all the member interfaces. If you add member interfaces to the EtherChannel and then configure
auto-IP on the EtherChannel, auto-IP TLV information is carried to all the member interfaces.
Attention
LLDP must be enabled on the member interfaces.
IP Addressing: IPv4 Addressing Configuration Guide
48
Auto-IP
Seed Device
• The list of EtherChannel member interfaces are maintained in ring interfaces corresponding to the
EtherChannel. Auto-IP information is transmitted on all the EtherChannel member interfaces.
• If you remove a member interface from an EtherChannel, auto-IP TLV information is not carried to the
removed interface.
Auto-IP on SVI interfaces
Some points on auto-IP configuration on a Switch Virtual Interface (SVI) are noted below:
• Auto-IP configuration on an SVI is possible only if a single physical interface is associated with an SVI.
• The SVI physical interface must be an access port or trunk port with only one associated VLAN or a
bridge domain interface (BDI).
• If the SVI is mapped to more than one physical port, then the auto-IP configuration on the SVI will be
removed.
Seed Device
Seed devices are the devices used to initiate network discovery. To initiate auto-IP capability in a ring, at least
one device must be configured as a seed device in the ring. To configure a device as a seed device in an auto-IP
ring, you must manually configure the IP address configured on one of its node interfaces with the auto-IP
address of the interface, with the mask /31 (or 255.255.255.254).
A sample topology is given below. In this scenario, device R1 is being configured as the seed device.
The e0/0 interface on device R1 is configured with the auto-IP address 10.1.1.1 and the e0/1 interface on
device R2 is configured with the auto-IP address 10.1.1.3.
To configure R1 as the seed device, 10.1.1.1 must be configured as the IP address of the interface e0/0. By
configuring the IP address of e0/0 interface of R1 to its auto-IP address, R1 is configured as the seed device
and the interface e0/0 becomes the owner of the subnet.
The process of configuring the device R1 as the seed device is given below:
After a connection is established between the devices R1 and R2, R1 sends a Link Layer Discovery
Protocol(LLDP) packet which contains an auto-IP Type Length Value (TLV) with priority 2.
The auto-IP information for the e0/0 interface on R1 is given below:
Interface IP address
Auto-IP address
Priority
10.1.1.1
10.1.1.1
2
On receiving the auto-IP TLV from R1, R2 derives the IP address for the interface e0/1 (by subtracting 1 from
the last octet of R1's auto-IP address), and assigns the IP address 10.1.1.0/31 to R2's e0/1 interface. The
interface e0/1 on R2 becomes the non-owner interface on this subnet.
IP Addressing: IPv4 Addressing Configuration Guide
49
Auto-IP
Auto-IP Configuration for Inserting a Device into an Auto-IP Ring
The IP address allocation is displayed in the illustration given below:
The device and node interface details for the subnet are given below:
Note
Device
Interface
IP address
Designation
R1
e0/0
10.1.1.1/31
Owner
R2
e0/1
10.1.1.0/31
Non-owner
Since the auto-IP address configured on the e0/1 interface on R2 is 10.1.1.3, the other node interface of
R2 is designated as the owner interface and 10.1.1.3 is automatically configured as the interface IP address
of the other node interface.
Auto-IP Configuration for Inserting a Device into an Auto-IP Ring
To insert a device into an existing auto-IP ring, the node interfaces of the device must be configured with the
auto-IP address.
Note
You can also configure the auto-IP feature on node interfaces that are part of an existing, but non-auto-IP
ring.
The topology in the illustration below shows a sample scenario.
Device R1 is configured as the seed device. Interface e0/0 on R1 is configured with the IP address 10.1.1.1/31,
and is the owner of the subnet connecting R1 and R2. Interface e0/1 on device R2 has the IP address 10.1.1.0/31,
and is the non-owner interface of the subnet.
Device R3 is inserted between R1 and R2. The two designated node interfaces e0/0 and e0/1 of R3 are
configured with the auto-IP address 10.1.1.5. After insertion of the device, the ring topology appears as shown
in the illustration below:
IP Addressing: IPv4 Addressing Configuration Guide
50
Auto-IP
Auto-IP Configuration for Inserting a Device into an Auto-IP Ring
Auto-IP TLV exchange between the devices R1 and R3 is given below:
1 R1 sends an auto-IP Type Length Value (TLV) with priority 2 to the e0/0 interface of R3.
2 After receiving the auto-IP TLV from R1, R3 sends an auto-IP TLV with priority 0 to the e0/0 interface
of R1.
3 R1 wins the election process and the interface e0/0 of R1 is designated as the owner interface on the subnet
connecting R1 and R3.
4 The e0/0 interface on R3 becomes the non-owner interface and the IP address 10.1.1.0 is assigned to it.
5 The other node interface on R3 is designated as an owner interface and its auto-IP address (10.1.1.5) is
assigned as the IP address of the interface.
Auto-IP TLV exchange between the devices R3 and R2 is given below:
1 R3 sends an auto-IP TLV with priority 2 to the e0/1 interface of R2.
2 After receiving the auto-IP TLV from R3, R2 sends an auto-IP TLV with priority 0 to the e0/1 interface
of R3.
3 R3 wins the election process and its interface e0/1 is designated as the owner interface on the subnet
connecting R3 and R2.
4 The e0/1 interface on R2 is designated as the non-owner interface, and the IP address 10.1.1.4 is assigned
to it.
5 The other node interface on R2 is designated as the owner interface and its auto-IP address is assigned as
the IP address.
The IP addresses that are configured for the owner and non-owner interfaces on the devices R1, R2, and R3
are given below:
Device
Interface
IP Address
Designation
R1
e0/0
10.1.1.1/31
Owner
R3
e0/0
10.1.1.0/31
Non-owner
R3
e0/1
10.1.1.5/31
Owner
R2
e0/1
10.1.1.4/31
Non-owner
IP Addressing: IPv4 Addressing Configuration Guide
51
Auto-IP
Device Removal from an Auto-IP Ring
Device Removal from an Auto-IP Ring
You can manually remove a device from an existing auto-IP ring.
Note
No configuration is required if you remove a device from an auto-IP ring and connect its neighbor devices.
The topology in the illustration below shows a sample scenario:
In the topology, device R3 is removed from the auto-IP ring and device R1 is connected to R2. As a result,
auto-IP Type Length Value (TLVs) are exchanged between R1 and R2. Since the e0/0 interface of R1 sends
an auto-IP TLV with priority 2 and the e0/1 interface of R2 sends an auto-IP TLV with priority 0 to the e0/0
interface on R1, the e0/0 interface of R1 is designated as the owner interface on the subnet connecting R1 and
R2. R1 assigns the IP address to the e0/1 interface on R2, and it becomes the non-owner interface on this
subnet.
After the removal of R3 from the auto-IP ring, the ring topology looks like this:
The IP address of the owner and non-owner interfaces on the subnet are given below:
Device
Interface
Designation
R1
e0/0
Owner
R2
e0/1
Non-owner
Conflict Resolution Using the Auto-Swap Technique
The auto-swap technique automatically resolves conflicts due to incorrect insertion of a device into an auto-IP
ring.
If you remove a device from an auto-IP ring, the owner and non-owner auto-IP configuration on the node
interfaces is retained. You can insert the device back into an auto-IP ring.
IP Addressing: IPv4 Addressing Configuration Guide
52
Auto-IP
Conflict Resolution Using the Auto-Swap Technique
If you incorrectly insert a device into a ring with its interfaces swapped (due to which two owner interfaces
and two non-owner interfaces are connected to each other, rather than a connection between an owner and a
non-owner interface), then identical priority values are exchanged between interfaces during the auto-IP Type
Length Value (TLV) transmission. This leads to a tie in the priority value that is exchanged between the node
interfaces of the inserted device, and a conflict is detected.
The auto-swap technique resolves conflicts on both the node interfaces of the inserted device and allows
allocation of IP addresses for the interfaces.
Note
No configuration is required to enable the auto-swap technique; it is enabled automatically. The auto-swap
technique is used only when conflict is detected on both the node interfaces of the device.
The topology in the illustration below shows a sample scenario:
In this topology, device R3 is incorrectly inserted between the devices R1 and R2, with its interfaces swapped.
The conflict arises due to incorrect insertion, as given below:
• An owner interface is connected to another owner interface; the e0/0 interface of R1 is connected to the
e0/1 interface of R3.
• A non-owner interface is connected to another non-owner interface; the e0/1 interface of R2 is connected
to the e0/0 interface of R3.
The auto-IP TLV exchange details between R1 and R3 are given below:
• The e0/0 interface on R1 sends an auto-IP TLV with priority 2 to the e0/1 interface on R3.
• The e0/1 interface on R3 sends an auto-IP TLV with priority 2 to the e0/0 interface on R1.
Since the same priority value of 2 is sent in both instances, there is a tie during the election process, leading
to a conflict.
Similarly, the same priority value of 0 is exchanged between the e0/0 interface of R3 and the e0/1 interface
of R2 since they are non-owner interfaces, leading to a conflict.
Auto Swap
The auto-IP feature uses the auto-swap technique to resolve conflicts on both the node interfaces of the inserted
device.
The priority and the interface IP address of the e0/1 interface on R3 is swapped with the priority and the
interface IP address of the e0/0 interface on R3, respectively.
After swapping, the following auto-IP TLV information is exchanged between R1 and R3:
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Auto-IP
How to Configure Auto-IP
• The e0/0 interface on R1 sends an auto-IP TLV with priority 2 to the e0/1 interface on R3.
• The e0/1 interface on R3 sends an auto-IP TLV with priority 0 to the e0/0 interface on R1.
Since the priority sent by R1 to R3 is higher than the priority sent by the interface e0/1 on R3, R3 derives the
IP address 10.1.1.0 for the e0/1 interface from the auto-IP address of R1 (10.1.1.1).
The following auto-IP TLV information is exchanged between R3 and R2:
• The e0/0 interface on R3 sends an auto-IP TLV with priority 2 to the e0/1 interface on R2.
• The e0/1 interface on R2 sends an auto-IP TLV with priority 0 to the e0/1 interface on R3.
R2 detects the priority sent by R3 to be higher than the priority sent by its interface e0/1 and derives the IP
address 10.1.1.4 from the auto-IP address of R3 (10.1.1.5).
After conflict resolution, the topology looks like this:
The e0/1 interface on R3 is designated as a non-owner interface and the e0/0 interface on R3 is designated as
the owner interface.
How to Configure Auto-IP
Configuring a Seed Device
You must configure at least one seed device in an auto-IP ring. To configure a seed device, you must configure
the auto-IP address on the two node interfaces of the device (for a specific ring), and use the same IP address
to configure the IP address on one of the two node interfaces.
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54
Auto-IP
Configuring a Seed Device
Attention
Understand these concepts before configuring auto-IP on virtual routing and forwarding instance (VRF)
interfaces, Switch Virtual Interfaces (SVIs), and EtherChannels:
• VRF—If you intend to enable auto-IP on a VRF interface, ensure that the node interface is presently
within the VRF. If the interface is not within a VRF presently, assign the interface to the VRF and
then configure auto-IP on the VRF interface. Ensure that both node interfaces for the ring are assigned
to the same VRF.
• SVI—Auto-IP configuration on an SVI is possible only if a single physical interface is associated
with an SVI and the physical interface is an access port.
• EtherChannels—You can configure auto-IP on an EtherChannel interface, but not on a member
interface of the EtherChannel.
SUMMARY STEPS
1. enable
2. configure terminal
3. lldp run
4. interface type number
5. auto-ip-ring ring-id ipv4-address auto-ip-address
6. exit
7. interface type number
8. auto-ip-ring ring-id ipv4-address auto-ip-address
9. ip address interface-ip-address subnet-mask
10. end
11. show auto-ip-ring [ring-id][detail]
DETAILED STEPS
Step 1
Command or Action
Purpose
enable
Enables privileged EXEC mode.
Example:
• Enter your password if prompted.
Device> enable
Step 2
configure terminal
Enters global configuration mode.
Example:
Device# configure terminal
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Auto-IP
Configuring a Seed Device
Step 3
Command or Action
Purpose
lldp run
Enables Link Layer Discovery Protocol (LLDP) for the
device.
Example:
Device(config)# lldp run
Step 4
interface type number
Specifies an interface type and number, and enters
interface configuration mode.
Example:
Device(config)# interface ethernet 0/0
Step 5
auto-ip-ring ring-id ipv4-address auto-ip-address
Configures the auto-IP address on the specified interface.
Example:
Device(config-if)# auto-ip-ring 4 ipv4-address
10.1.1.1
Step 6
exit
Exits interface configuration mode and enters global
configuration mode.
Example:
Device(config-if)# exit
Step 7
interface type number
Specifies an interface type and number, and enters
interface configuration mode.
Example:
Device(config)# interface ethernet 0/1
Step 8
auto-ip-ring ring-id ipv4-address auto-ip-address
Configures the auto-IP address on the specified interface.
Example:
Device(config-if)# auto-ip-ring 4 ipv4-address
10.1.1.1
Step 9
ip address interface-ip-address subnet-mask
Example:
Configures the IP address on the specified interface.
Note
The specified interface is designated as the
owner interface of the seed device.
Device(config-if)# ip address 10.1.1.1
255.255.255.254
Step 10
end
Example:
Device(config-if)# end
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56
Returns to privileged EXEC mode.
Auto-IP
Configuring the Auto-IP Functionality on Node Interfaces (for Inclusion in an Auto-IP Ring)
Step 11
Command or Action
Purpose
show auto-ip-ring [ring-id][detail]
Displays auto-IP information.
Example:
Device# show auto-ip-ring 4 detail
Configuring the Auto-IP Functionality on Node Interfaces (for Inclusion in an
Auto-IP Ring)
To insert a device into an auto-IP ring or to enable node interfaces in an existing ring, you must configure the
auto-IP address on the 2 designated node interfaces of the device.
Attention
Understand these concepts before configuring auto-IP on virtual routing and forwarding instance (VRF)
interfaces, Switch Virtual Interfaces (SVIs), and EtherChannels:
• VRF—If you intend to enable auto-IP on a VRF interface, ensure that the node interface is presently
within the VRF. If the interface is not within a VRF presently and you want the interface to be within
a VRF, move the interface within the VRF and then configure auto-IP on the VRF interface. Ensure
that both node interfaces are within the same VRF.
• SVI—Auto-IP configuration on an SVI is possible only if a single physical interface is associated
with an SVI and the physical interface is an access port.
• EtherChannels—You can configure auto-IP on an EtherChannel interface, but not on a member
interface of the EtherChannel.
This task is applicable for a non-seed device in an auto-IP ring. Ensure that a seed device is configured
for the auto-IP ring before performing this task.
Perform the steps given below to configure the auto-IP functionality on the two node interfaces of a device:
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57
Auto-IP
Configuring the Auto-IP Functionality on Node Interfaces (for Inclusion in an Auto-IP Ring)
SUMMARY STEPS
1. enable
2. configure terminal
3. lldp run
4. interface type number
5. auto-ip-ring ring-id ipv4-address auto-ip-address
6. exit
7. interface type number
8. auto-ip-ring ring-id ipv4-address auto-ip-address
9. end
10. show auto-ip-ring [ring-id][detail]
DETAILED STEPS
Step 1
Command or Action
Purpose
enable
Enables privileged EXEC mode.
Example:
• Enter your password if prompted.
Device> enable
Step 2
configure terminal
Enters global configuration mode.
Example:
Device# configure terminal
Step 3
lldp run
Enables Link Layer Discovery Protocol (LLDP) for the
device.
Example:
Device(config)# lldp run
Step 4
interface type number
Specifies an interface type and number, and enters
interface configuration mode.
Example:
Device(config)# interface ethernet 0/1
Step 5
auto-ip-ring ring-id ipv4-address auto-ip-address
Example:
Device(config-if)# auto-ip-ring 4 ipv4-address
10.1.1.3
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58
Configures the auto-IP address on the specified interface.
Auto-IP
Verifying and Troubleshooting Auto-IP
Step 6
Command or Action
Purpose
exit
Exits interface configuration mode and enters global
configuration mode.
Example:
Device(config-if)# exit
Step 7
interface type number
Specifies an interface type and number, and enters
interface configuration mode.
Example:
Device(config)# interface ethernet 1/1
Step 8
auto-ip-ring ring-id ipv4-address auto-ip-address
Configures the auto-IP address on the specified interface.
Example:
Device(config-if)# auto-ip-ring 4 ipv4-address
10.1.1.3
Step 9
Returns to privileged EXEC mode.
end
Example:
Device(config-if)# end
Step 10
show auto-ip-ring [ring-id][detail]
Displays auto-IP information.
Example:
Device# show auto-ip-ring 4 detail
Verifying and Troubleshooting Auto-IP
Perform this task to verify auto-IP functions.
Note
The commands are not in any specific order. The show auto-ip-ring command is presented twice. One
of the examples displays auto-IP ring information for virtual routing and forwarding instance (VRF)
interfaces, and the other example displays auto-IP ring information for non-VRF interfaces.
SUMMARY STEPS
1. enable
2. show auto-ip-ring [ring-id][detail]
3. show auto-ip-ring [ring-id][detail]
4. debug auto-ip-ring {ring-id {errors | events} |errors | events}
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Auto-IP
Verifying and Troubleshooting Auto-IP
DETAILED STEPS
Step 1
enable
Enables privileged EXEC mode.
Example:
Device> enable
Step 2
show auto-ip-ring [ring-id][detail]
This command displays auto-IP ring information for a specific device or auto-IP ring.
Example:
Device# show auto-ip-ring
Step 3
Auto-IP ring 1
Auto-IP Address
: 10.1.1.5
Ring Port0
My Current-IP
My Priority
: Ethernet0/0
: 0.0.0.0
: 1
Auto-IP ring 3
Auto-IP Address
: 10.1.1.3
Ring Port0
My Current-IP
My Priority
: Ethernet0/1
: 0.0.0.0
: 1
show auto-ip-ring [ring-id][detail]
This command displays auto-IP ring information for VRF interfaces.
Example:
Device# show auto-ip-ring detail
Auto-IP ring 7
Auto-IP Address
: 10.1.1.11
VRF Name
Ring Port1
My Current-IP
My Priority
:
:
:
:
Rx Auto-IP Address
Rx Current-IP
Rx Priority
: 10.1.1.13
: 10.1.1.10
: 0
VRF Name
Ring Port0
My Current-IP
My Priority
:
:
:
:
Rx Auto-IP Address
Rx Current-IP
Rx Priority
: 10.1.1.9
: 10.1.1.9
: 2
3
Ethernet1/1
10.1.1.11
2
3
Ethernet1/0
10.1.1.8
0
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Auto-IP
Configuration Examples for Auto-IP
Step 4
debug auto-ip-ring {ring-id {errors | events} |errors | events}
This command debugs errors and events for the specified auto-IP ring.
Example:
Device# debug auto-ip-ring 1 errors
Auto IP Ring errors debugging is on for the ring id : 1
*Jul 26 11:30:40.541: (Ethernet0/0) priority (value:1) conflict detected,
Note
need admin intervention
A conflict is detected in the above debug example because the priority in the auto-IP Type Length Value (TLV)
that is sent from the interface and the priority that is received from the neighbor interface is the same.
Configuration Examples for Auto-IP
Example: Configuring a Seed Device
Device> enable
Device# configure terminal
Device(config)# lldp run
Device(config)# interface ethernet 0/0
Device(config-if)# auto-ip-ring 4 ipv4-address 10.1.1.1
Device(config-if)# exit
Device(config)# interface ethernet 1/0
Device(config-if)# auto-ip-ring 4 ipv4-address 10.1.1.1
Device(config-if)# ip address 10.1.1.1 255.255.255.254
Device(config-if)# end
Example: Configuring the Auto-IP Functionality on Node Interfaces (for
Inclusion in an Auto-IP Ring)
Device> enable
Device# configure terminal
Device(config)# lldp run
Device(config)# interface ethernet 0/1
Device(config-if)# auto-ip-ring 4 ipv4-address 10.1.1.3
Device(config-if)# exit
Device(config)# interface ethernet 1/1
Device(config-if)# auto-ip-ring 4 ipv4-address 10.1.1.3
Device(config-if)# end
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61
Auto-IP
Additional References for Auto-IP
Additional References for Auto-IP
Related Documents
Related Topic
Document Title
Configuring IPv4 Addresses
IP Addressing: IPv4 Addressing Configuration Guide
Using Link Layer Discovery Protocol in Multivendor Carrier Ethernet Configuration Guide
Networks
IPv4 Addressing commands
Cisco IOS IP Addressing Services Command
Reference
Cisco IOS commands
Cisco IOS Master Command List, All Releases
Technical Assistance
Description
Link
The Cisco Support and Documentation website
http://www.cisco.com/cisco/web/support/index.html
provides online resources to download documentation,
software, and tools. Use these resources to install and
configure the software and to troubleshoot and resolve
technical issues with Cisco products and technologies.
Access to most tools on the Cisco Support and
Documentation website requires a Cisco.com user ID
and password.
IP Addressing: IPv4 Addressing Configuration Guide
62
Auto-IP
Feature Information for Auto-IP
Feature Information for Auto-IP
Table 13: Feature Information for Auto-IP
Feature Name
Releases
Feature Information
Auto-IP
Cisco IOS XE
Release 3.10(S)
The auto-IP feature addresses the problem of manually
reconfiguring nodes during insertion, deletion, and
movement of nodes within an auto-IP ring. The auto-IP
feature automatically provides IP addresses to the node
interfaces inserted into an auto-IP ring.
In Cisco IOS XE Release 3.10(S), it is not possible to
configure the auto-IP feature on virtual routing and
forwarding instance (VRF) interfaces, SVIs, and
EtherChannels.
The following commands were introduced or modified:
auto-ip-ring, debug auto-ip-ring, show auto-ip-ring.
Cisco IOS XE
Release 3.12(S)
In Cisco IOS XE Release 3.12(S), the auto-IP feature is
enhanced to support auto-IP configuration on virtual routing
and forwarding instance (VRF) interfaces, SVIs, and
EtherChannels.
The following commands were introduced or modified:
show auto-ip-ring.
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63
Auto-IP
Feature Information for Auto-IP
IP Addressing: IPv4 Addressing Configuration Guide
64
CHAPTER
6
Zero Touch Auto-IP
The Zero touch Auto-IP feature enables automatic allocation and configuration of IP addresses for nodes in
a ring topology. The IP addresses are allocated from a pool of IP addresses that is predefined by you.
The advantages of Zero Touch Auto-IP over Auto-IP are:
• IP addresses can be configured automatically on ring nodes. Manual IP address configuration is not
required on each node.
• IP addresses are allocated from a common IP address pool, and the IP address range can be predefined
by you.
• Finding Feature Information, page 65
• Prerequisites for Zero Touch Auto-IP, page 66
• Restrictions for Zero Touch Auto-IP, page 66
• Information About Zero Touch Auto-IP, page 66
• How to Configure Zero Touch Auto-IP, page 68
• Configuration Examples for Zero Touch Auto-IP, page 77
• Additional References for Zero Touch Auto-IP, page 78
• Feature Information for Auto-IP, page 78
Finding Feature Information
Your software release may not support all the features documented in this module. For the latest caveats and
feature information, see Bug Search Tool and the release notes for your platform and software release. To
find information about the features documented in this module, and to see a list of the releases in which each
feature is supported, see the feature information table at the end of this module.
Use Cisco Feature Navigator to find information about platform support and Cisco software image support.
To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.
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65
Zero Touch Auto-IP
Prerequisites for Zero Touch Auto-IP
Prerequisites for Zero Touch Auto-IP
• Link Layer Discovery Protocol (LLDP) must be enabled on all the Auto-IP ring device ports.
• In an Auto-IP ring, you must identify one Auto-IP device as an Auto-IP server.
• None of the ports identified to be part of the Zero Touch Auto-IP ring should be manually configured
with the Auto-IP functionality. If a port that is identified for Zero touch Auto-IP configuration has a
manual Auto-IP configuration, disable the manual Auto-IP configuration on that port.
Restrictions for Zero Touch Auto-IP
• Zero Touch Auto-IP and Auto-IP cannot coexist. To implement Zero Touch Auto-IP functionality, all
the ports of the Auto-IP ring have to be configured as Zero Touch Auto-IP ports.
• Zero Touch Auto-IP works if the designated Auto-IP server is in an autonomic network.
Information About Zero Touch Auto-IP
The Zero Touch Auto-IP feature uses Autonomic Networking and Link Layer Discovery Protocol (LLDP) to
achieve the objective of automatic IP address configuration on nodes in a ring network.
Consider the topology for Zero Touch Auto-IP configuration. The devices R1, R2, R3 and R4 are connected
in a ring network and LLDP is enabled on all the ring ports.
Figure 7: Zero Touch Auto-IP Topology
To know about and configure the Zero touch Auto-IP functionality, use the information given below:
1 Associate one device in the ring network (say R1) to the autonomic network. Enable autonomic status for
the other Auto-IP devices. For more information on autonomic networks, refer Autonomic Networking.
R1(config)# autonomic registrar
R1(config-registrar)# domain-id auto-addressing.com
R1(config-registrar)# no shutdown
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Zero Touch Auto-IP
Information About Zero Touch Auto-IP
R1(config-registrar)# CA local
R1(config-registrar)# exit
R1(config)# autonomic
R2(config)# autonomic
R3(config)# autonomic
R4(config)# autonomic
Note that R1 is configured on the registrar and receives a certificate. The remaining devices are configured
as autonomic devices.
2 Enable the auto mode on all the ports in the ring to enable automatic IP address configuration. Auto mode
must be enabled on the e0/0 and e0/1 ports on R1, R2, R3 and R4. For ports of the same device, the ring
ID must be identical.
Device(config-if)# auto-ip-ring 1 ipv4-auto
3 Configure the device added to the autonomic network (R1) as the Auto-IP server. The server stores a pool
of IP addresses.
R1(config)# auto-ip-ring server
4 Reserve a pool of IP addresses on the Auto-IP server for IP address allocation to the ring ports.
Note
In Zero Touch and manual Auto-IP configuration, a /31 subnet is created for a pair of owner and nonowner
ports (each device will have a owner and non owner port). An odd-numbered IP address (such as 10.1.1.11)
is issued to an owner port and an even-numbered IP address (10.1.1.10) is reserved for a nonowner port.
Therefore, specify the first IP address in the range along with the number of devices (or /31 subnets) that
make up the Auto-IP ring
R1(config-auto-ip-server)# ipv4-address-pool 10.1.1.10 6
Result—A range of IP addresses from 10.1.1.10 to 10.1.1.21 is allocated for the Auto-IP ring. The Auto-IP
server is added to the autonomic network and is reachable by other nodes in the autonomic network.
Note
IP addresses for six devices will be reserved (though the requirement is for four devices); the additional
IP addresses will be allocated when you add new devices to the ring.
5 Auto-IP negotiation process— IP addresses are allocated to the Auto-IP ring nodes through a negotiation
process. To initiate the process, configure one port as the seed port in the Auto-IP ring.
R1(config-if)# auto-ip-ring 1 ipv4-seed
The negotiation process is explained below:
1 The priority of the seed port (a port on R1, for example) is set to 2 and it is made an owner port. An
IP address from the reserved pool is configured on the port.
2 The seed port advertises its priority (2) to its connected neighbor, and makes the neighbor port a non
owner. The seed port assigns an IP address to the neighbor port and the neighbor port's priority is
changed to 0.
3 Each owner port in the ring gets an IP address from the Auto IP server. The owner port, in turn, assigns
an IP address to the connected neighbor port.
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67
Zero Touch Auto-IP
How to Configure Zero Touch Auto-IP
6 Auto-IP communication—After initial configuration, each owner port sends periodic messages to the
Auto-IP server to continue preserving its IP address. If there is no message from the owner port to the
Auto-IP server for 15 minutes, the server moves the IP address to the pool of free IP addresses.
The following are some points to keep in mind in the context of Zero Touch Auto-IP configuration:
• LLDP has to be enabled on all the Auto-IP ring ports before Auto-IP configuration.
• Before you insert a new interface into the ring, configure auto mode on the ring ports.
• For Zero Touch Auto-IP configuration, the number of devices (or /31 subnets) that make up the Auto-IP
ring must be between 1 and 128.
• When you specify a pool of IP addresses, ensure that IP addresses in the specified range are not already
in use.
• Ensure that you reserve some additional IP addresses for the Auto-IP ring, in case more devices are
added to the ring topology at a later point in time.
• The starting IP address used for the Auto-IP address pool reservation must be an even number. For
example, 10.1.1.10 is a valid IP address but 10.1.1.9 is not.
• If you remove a device from an Auto-IP ring, the Auto-IP addresses are released back to the Auto-IP
server.
How to Configure Zero Touch Auto-IP
Associating an Auto-IP Server with an Autonomic Network
The Auto-IP server (R1) must be associated with the autonomic network, and configured in the Autonomic
Network registrar. The other devices in the network (R2, R3, and R4) must be enabled with the autonomic
status.
SUMMARY STEPS
1. enable
2. configure terminal
3. autonomic registrar
4. domain-id auto-addressing.com
5. no shutdown
6. CA local
7. exit
8. autonomic
9. autonomic
10. autonomic
11. autonomic
12. exit
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Zero Touch Auto-IP
Associating an Auto-IP Server with an Autonomic Network
DETAILED STEPS
Step 1
Command or Action
Purpose
enable
Enables privileged EXEC mode.
Example:
• Enter your password if prompted.
R1> enable
Step 2
configure terminal
Enters global configuration mode.
Example:
R1# configure terminal
Step 3
autonomic registrar
Enables the Auto-IP server in the Autonomic Network registrar
and enters registrar configuration mode.
Example:
R1(config)# autonomic registrar
Step 4
domain-id auto-addressing.com
Example:
Represents a common group of all devices registering with the
registrar.
Note
If R1 is configured on the AN registrar, then R1
represents the Auto-IP ring devices R2, R3, and R4.
R1(config-registrar)# domain-id
auto-addressing.com
Step 5
no shutdown
Enables the autonomic registrar.
Example:
R1(config-registrar)# no shutdown
Step 6
CA local
Issues a Local CA certificate to the Auto-IP server.
Example:
R1(config-registrar)# CA local
Step 7
exit
Exits registrar configuration mode and enters global
configuration mode.
Example:
R1(config-registrar)# exit
Step 8
autonomic
Configures the Auto-IP server as an autonomic device.
Note
Example:
R1(config)# autonomic
You should associate the remaining devices (R2, R3,
and R4) in the Auto-IP ring with the autonomic
network, as given in the next few steps.
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Zero Touch Auto-IP
Enabling Auto Mode on Auto-IP Ring Ports
Step 9
Command or Action
Purpose
autonomic
Configures R2 as an autonomic device.
Example:
R2(config)# autonomic
Step 10
autonomic
Configures R3 as an autonomic device.
Example:
R3(config)# autonomic
Step 11
autonomic
Configures R4 as an autonomic device.
Example:
R4(config)# autonomic
Step 12
Exits global configuration mode and enters privileged EXEC
mode.
exit
Example:
Device(config)# exit
What to Do Next
Enable auto mode on Auto-IP ring ports
Enabling Auto Mode on Auto-IP Ring Ports
Before You Begin
Identify the ports that will be part of the Auto-IP ring. Remember that you must enable Auto mode on all the
ports in an Auto-IP ring.
SUMMARY STEPS
1. enable
2. configure terminal
3. lldp run
4. interface type number
5. auto-ip-ring ring-id ipv4-auto
6. exit
7. Repeat steps to configure auto mode on each Auto-IP ring port.
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Zero Touch Auto-IP
Enabling Auto Mode on Auto-IP Ring Ports
DETAILED STEPS
Step 1
Command or Action
Purpose
enable
Enables privileged EXEC mode.
• Enter your password if prompted.
Example:
Device> enable
Step 2
configure terminal
Enters global configuration mode.
Example:
Device# configure terminal
Step 3
lldp run
Enables Link Layer Discovery Protocol (LLDP) for the
device.
Example:
Device(config)# lldp run
Step 4
interface type number
Specifies an interface type and number, and enters
interface configuration mode.
Example:
Device(config)# interface ethernet 0/0
Step 5
auto-ip-ring ring-id ipv4-auto
Configures auto mode on the Auto-IP ring port.
Example:
Device(config-if)# auto-ip-ring 1 ipv4-auto
Step 6
exit
Exits interface configuration mode and enters global
configuration mode.
Example:
Device(config-if)# exit
Step 7
Repeat steps to configure auto mode on each Auto-IP
ring port.
---
What to Do Next
Configure an Auto-IP server and reserve a pool of IP addresses for the Auto-IP ring ports.
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71
Zero Touch Auto-IP
Configuring an Auto-IP Server and Reserving a Pool of IP Addresses on the Server
Configuring an Auto-IP Server and Reserving a Pool of IP Addresses on the
Server
Before You Begin
Ensure that all ports of the ring are identified and auto mode is enabled on the ports.
SUMMARY STEPS
1. enable
2. configure terminal
3. auto-ip-ring server
4. ipv4-address-pool auto-ipv4-address number-of-subnets
5. exit
DETAILED STEPS
Step 1
Command or Action
Purpose
enable
Enables privileged EXEC mode.
Example:
• Enter your password if prompted.
Device> enable
Step 2
configure terminal
Enters global configuration mode.
Example:
Device# configure terminal
Step 3
auto-ip-ring server
Configures the device as an Auto-IP server and enters Auto-IP
server configuration mode.
Example:
Device(config)# auto-ip-ring server
Step 4
ipv4-address-pool auto-ipv4-address
number-of-subnets
Example:
Device(config-auto-ip-server)#
ipv4-address-pool 10.1.1.10 6
Step 5
exit
Example:
Device(config-auto-ip-server)# exit
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Reserves a pool of IP addresses on the Auto-IP server.
The number of subnets should, at a minimum, be the total number
of owner ports or devices in the ring. The odd-numbered IP
addresses are assigned to the owner ports, and each non owner port
fetches its IP address from the owner port through LLDP
Exits Auto-IP server configuration mode and enters global
configuration mode.
Zero Touch Auto-IP
Configuring a Seed Port
What to Do Next
Configure a seed port to start the Auto-IP negotiation process.
Configuring a Seed Port
Before You Begin
Ensure all the Auto-IP ports are in auto mode, and a pool of IP addresses is reserved for the Auto-IP ports.
SUMMARY STEPS
1. enable
2. configure terminal
3. interface type number
4. auto-ip-ring ring-id ipv4-seed
5. exit
6. end
7. show auto-ip-ring [ring-id][detail]
DETAILED STEPS
Step 1
Command or Action
Purpose
enable
Enables privileged EXEC mode.
Example:
• Enter your password if prompted.
Device> enable
Step 2
configure terminal
Enters global configuration mode.
Example:
Device# configure terminal
Step 3
interface type number
Specifies an interface type and number, and enters
interface configuration mode.
Example:
Device(config)# interface ethernet 0/1
Step 4
auto-ip-ring ring-id ipv4-seed
Designates the port as the seed port and initiates the
Auto-IP negotiation process.
Example:
Device(config-if)# auto-ip-ring 1 ipv4-seed
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Zero Touch Auto-IP
Verifying and Troubleshooting Zero Touch Auto-IP
Step 5
Command or Action
Purpose
exit
Exits interface configuration mode and enters global
configuration mode.
Example:
Device(config-if)# exit
Step 6
Returns to privileged EXEC mode.
end
Example:
Device(config-if)# end
Step 7
show auto-ip-ring [ring-id][detail]
Displays auto-IP information.
Example:
Device# show auto-ip-ring 4 detail
What to Do Next
Verify if the IP addresses have been configured.
Verifying and Troubleshooting Zero Touch Auto-IP
Perform this task to verify Zero touch Auto-IP functions.
Note
The commands are not in any specific order.
SUMMARY STEPS
1. enable
2. show auto-ip-ring [ring-id][detail]
3. show autonomic service
4. show autonomic device
5. show autonomic neighbors
6. debug auto-ip-ring {ring-id {errors | events} |errors | events}
DETAILED STEPS
Step 1
enable
Enables privileged EXEC mode.
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Zero Touch Auto-IP
Verifying and Troubleshooting Zero Touch Auto-IP
Example:
Device> enable
Step 2
show auto-ip-ring [ring-id][detail]
This command displays Auto-IP ring information for a specific device or Auto-IP ring. The sample output given below
displays two ports representing a ring, their IP addresses, and the connected ports and IP addresses (neighboring port
information is denoted by Rx).
Example:
Device# show auto-ip-ring 1
Auto-IP ring 1
Step 3
Auto-IP Address
: 10.1.1.11
Ring Port0
My Current-IP
My Priority
: Ethernet0/1
: 10.1.1.11
: 2
Rx Auto-IP Address
Rx Current-IP
Rx-Priority
: 10.1.1.13
: 10.1.1.12
: 0
Ring Port1
My Current-IP
My Priority
: Ethernet0/0
: 10.1.1.10
: 0
Rx Auto-IP Address
Rx Current-IP
Rx-Priority
: 10.1.1.17
: 10.1.1.17
: 2
show autonomic service
The following is sample output from this command, and it displays autonomic services configured on a device connected
to an autonomic network.
Example:
Device# show autonomic service
Service
Autonomic registrar
ANR type
Auto IP Server
Step 4
IP-Addr
FD53:EE55:A541:0:AABB:CC00:100:1
IOS CA
FD53:EE55:A541:0:AABB:CC00:100:1
show autonomic device
The following is sample output from this command, and it displays autonomic network configuration credentials for a
device that is connected to the autonomic network. Details like unique identifier (UDI), device identifier (Device ID),
associated domain (Domain ID), and so on, are displayed.
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Zero Touch Auto-IP
Verifying and Troubleshooting Zero Touch Auto-IP
Example:
Device# show autonomic device
UDI
Device ID
Domain ID
Domain Certificate
SN:655773698,cn=aabb.cc00.0100-2
Certificate Serial Number
Device Address
Domain Cert is Valid
Step 5
PID:Unix SN:655773698
aabb.cc00.0100-2
auto-networking.com
(sub:) ou=abcd.com+serialNumber=PID:Unix
03
FD53:EE55:A541:0:AABB:CC00:100:2
show autonomic neighbors
The following is sample output from this command, and it displays autonomic configuration details of connected, neighbor
devices. Details such as unique identifier (UDI), device identifier (Device ID), and associated domain (Domain ID), are
displayed.
Example:
Device# show autonomic neighbors
UDI
Device-ID
Domain
Interface
-------------------------------------------------------------------------------PID:Unix SN:655773697
aabb.cc00.0100-1
abcd.com
Ethernet0/0
PID:Unix SN:655773699
aabb.cc00.0100-4
abcd.com
Ethernet0/1
Step 6
debug auto-ip-ring {ring-id {errors | events} |errors | events}
The following is sample output from this command, and it displays debug errors and events for the specified Auto-IP
ring.
Note
A conflict is detected in the sample debug output below because the priority in the Auto-IP Type Length Value
(TLV) that is sent from the interface and the priority that is received from the neighbor interface are the same.
Example:
Device# debug auto-ip-ring 2 errors
Auto IP Ring errors debugging is on for the ring id : 2
*Jul 26 11:30:40.541: (Ethernet0/0) priority (value:1) conflict detected,
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need admin intervention
Zero Touch Auto-IP
Configuration Examples for Zero Touch Auto-IP
Configuration Examples for Zero Touch Auto-IP
Example: Associating an Auto-IP Server with an Autonomic Network
Auto-IP server (R1) is associated with the autonomic network. The other devices in the network (R2, R3, and
R4) are enabled with the autonomic status.
R1(config)# autonomic
R1(config-registrar)#
R1(config-registrar)#
R1(config-registrar)#
R1(config-registrar)#
R1(config)# autonomic
registrar
domain-id auto-addressing.com
no shutdown
CA local
exit
R2(config)# autonomic
R3(config)# autonomic
R4(config)# autonomic
Example: Enabling Auto Mode on Auto-IP Ring Ports
Device> enable
Device# configure terminal
Device(config)# lldp run
Device(config)# interface ethernet 0/0
Device(config-if)# auto-ip-ring 1 ipv4-auto
Device(config-if)# exit
Repeat the preceding steps to configure the auto mode on each Auto-IP ring port
Example: Configuring an Auto-IP Server and Reserving a Pool of IP Addresses
on the Server
Device> enable
Device# configure terminal
Device(config)# auto-ip-ring server
Device(config-auto-ip-server)# ipv4-address-pool 10.1.1.10 6
Device(config-auto-ip-server)# exit
Example: Configuring a Seed Port
Device> enable
Device# configure terminal
Device(config)# interface e0/0
Device(config-if)# auto-ip-ring 1 ipv4-seed
Device(config-if)# exit
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Zero Touch Auto-IP
Additional References for Zero Touch Auto-IP
Additional References for Zero Touch Auto-IP
Related Documents
Related Topic
Document Title
Auto-IP
IP Addressing: IPv4 Addressing Configuration Guide
Configuring IPv4 Addresses
IP Addressing: IPv4 Addressing Configuration Guide
Using Link Layer Discovery Protocol in Multivendor Carrier Ethernet Configuration Guide
Networks
IPv4 Addressing commands
Cisco IOS IP Addressing Services Command
Reference
Cisco IOS commands
Cisco IOS Master Command List, All Releases
Technical Assistance
Description
Link
The Cisco Support and Documentation website
http://www.cisco.com/cisco/web/support/index.html
provides online resources to download documentation,
software, and tools. Use these resources to install and
configure the software and to troubleshoot and resolve
technical issues with Cisco products and technologies.
Access to most tools on the Cisco Support and
Documentation website requires a Cisco.com user ID
and password.
Feature Information for Auto-IP
Table 14: Feature Information for Auto-IP
Feature Name
Releases
Feature Information
Zero Touch Auto-IP
Cisco IOS XE
Release 3.15S
The Zero Touch Auto-IP feature enables automatic
allocation and configuration of IP addresses for nodes in an
Auto-IP ring. The IP addresses are allocated from a pool of
IP addresses.
The following commands were introduced or modified:
auto-ip-ring ipv4-auto, auto-ip-ring ipv4-seed,
auto-ip-ring server, ipv4-address-pool.
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Zero Touch Auto-IP
Feature Information for Auto-IP
IP Addressing: IPv4 Addressing Configuration Guide
79
Zero Touch Auto-IP
Feature Information for Auto-IP
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